Now that MacOS terminal supports 256 colors I keep needing to know the Xterm/ANSI names. I found this list—copying it here for future reference.

Name ctermfg guifg RGB
x016_Grey0 ctermfg=16 guifg=#000000 “rgb=0,0,0
x017_NavyBlue ctermfg=17 guifg=#00005f “rgb=0,0,95
x018_DarkBlue ctermfg=18 guifg=#000087 “rgb=0,0,135
x019_Blue3 ctermfg=19 guifg=#0000af “rgb=0,0,175
x020_Blue3 ctermfg=20 guifg=#0000d7 “rgb=0,0,215
x021_Blue1 ctermfg=21 guifg=#0000ff “rgb=0,0,255
x022_DarkGreen ctermfg=22 guifg=#005f00 “rgb=0,95,0
x023_DeepSkyBlue4 ctermfg=23 guifg=#005f5f “rgb=0,95,95
x024_DeepSkyBlue4 ctermfg=24 guifg=#005f87 “rgb=0,95,135
x025_DeepSkyBlue4 ctermfg=25 guifg=#005faf “rgb=0,95,175
x026_DodgerBlue3 ctermfg=26 guifg=#005fd7 “rgb=0,95,215
x027_DodgerBlue2 ctermfg=27 guifg=#005fff “rgb=0,95,255
x028_Green4 ctermfg=28 guifg=#008700 “rgb=0,135,0
x029_SpringGreen4 ctermfg=29 guifg=#00875f “rgb=0,135,95
x030_Turquoise4 ctermfg=30 guifg=#008787 “rgb=0,135,135
x031_DeepSkyBlue3 ctermfg=31 guifg=#0087af “rgb=0,135,175
x032_DeepSkyBlue3 ctermfg=32 guifg=#0087d7 “rgb=0,135,215
x033_DodgerBlue1 ctermfg=33 guifg=#0087ff “rgb=0,135,255
x034_Green3 ctermfg=34 guifg=#00af00 “rgb=0,175,0
x035_SpringGreen3 ctermfg=35 guifg=#00af5f “rgb=0,175,95
x036_DarkCyan ctermfg=36 guifg=#00af87 “rgb=0,175,135
x037_LightSeaGreen ctermfg=37 guifg=#00afaf “rgb=0,175,175
x038_DeepSkyBlue2 ctermfg=38 guifg=#00afd7 “rgb=0,175,215
x039_DeepSkyBlue1 ctermfg=39 guifg=#00afff “rgb=0,175,255
x040_Green3 ctermfg=40 guifg=#00d700 “rgb=0,215,0
x041_SpringGreen3 ctermfg=41 guifg=#00d75f “rgb=0,215,95
x042_SpringGreen2 ctermfg=42 guifg=#00d787 “rgb=0,215,135
x043_Cyan3 ctermfg=43 guifg=#00d7af “rgb=0,215,175
x044_DarkTurquoise ctermfg=44 guifg=#00d7d7 “rgb=0,215,215
x045_Turquoise2 ctermfg=45 guifg=#00d7ff “rgb=0,215,255
x046_Green1 ctermfg=46 guifg=#00ff00 “rgb=0,255,0
x047_SpringGreen2 ctermfg=47 guifg=#00ff5f “rgb=0,255,95
x048_SpringGreen1 ctermfg=48 guifg=#00ff87 “rgb=0,255,135
x049_MediumSpringGreen ctermfg=49 guifg=#00ffaf “rgb=0,255,175
x050_Cyan2 ctermfg=50 guifg=#00ffd7 “rgb=0,255,215
x051_Cyan1 ctermfg=51 guifg=#00ffff “rgb=0,255,255
x052_DarkRed ctermfg=52 guifg=#5f0000 “rgb=95,0,0
x053_DeepPink4 ctermfg=53 guifg=#5f005f “rgb=95,0,95
x054_Purple4 ctermfg=54 guifg=#5f0087 “rgb=95,0,135
x055_Purple4 ctermfg=55 guifg=#5f00af “rgb=95,0,175
x056_Purple3 ctermfg=56 guifg=#5f00d7 “rgb=95,0,215
x057_BlueViolet ctermfg=57 guifg=#5f00ff “rgb=95,0,255
x058_Orange4 ctermfg=58 guifg=#5f5f00 “rgb=95,95,0
x059_Grey37 ctermfg=59 guifg=#5f5f5f “rgb=95,95,95
x060_MediumPurple4 ctermfg=60 guifg=#5f5f87 “rgb=95,95,135
x061_SlateBlue3 ctermfg=61 guifg=#5f5faf “rgb=95,95,175
x062_SlateBlue3 ctermfg=62 guifg=#5f5fd7 “rgb=95,95,215
x063_RoyalBlue1 ctermfg=63 guifg=#5f5fff “rgb=95,95,255
x064_Chartreuse4 ctermfg=64 guifg=#5f8700 “rgb=95,135,0
x065_DarkSeaGreen4 ctermfg=65 guifg=#5f875f “rgb=95,135,95
x066_PaleTurquoise4 ctermfg=66 guifg=#5f8787 “rgb=95,135,135
x067_SteelBlue ctermfg=67 guifg=#5f87af “rgb=95,135,175
x068_SteelBlue3 ctermfg=68 guifg=#5f87d7 “rgb=95,135,215
x069_CornflowerBlue ctermfg=69 guifg=#5f87ff “rgb=95,135,255
x070_Chartreuse3 ctermfg=70 guifg=#5faf00 “rgb=95,175,0
x071_DarkSeaGreen4 ctermfg=71 guifg=#5faf5f “rgb=95,175,95
x072_CadetBlue ctermfg=72 guifg=#5faf87 “rgb=95,175,135
x073_CadetBlue ctermfg=73 guifg=#5fafaf “rgb=95,175,175
x074_SkyBlue3 ctermfg=74 guifg=#5fafd7 “rgb=95,175,215
x075_SteelBlue1 ctermfg=75 guifg=#5fafff “rgb=95,175,255
x076_Chartreuse3 ctermfg=76 guifg=#5fd700 “rgb=95,215,0
x077_PaleGreen3 ctermfg=77 guifg=#5fd75f “rgb=95,215,95
x078_SeaGreen3 ctermfg=78 guifg=#5fd787 “rgb=95,215,135
x079_Aquamarine3 ctermfg=79 guifg=#5fd7af “rgb=95,215,175
x080_MediumTurquoise ctermfg=80 guifg=#5fd7d7 “rgb=95,215,215
x081_SteelBlue1 ctermfg=81 guifg=#5fd7ff “rgb=95,215,255
x082_Chartreuse2 ctermfg=82 guifg=#5fff00 “rgb=95,255,0
x083_SeaGreen2 ctermfg=83 guifg=#5fff5f “rgb=95,255,95
x084_SeaGreen1 ctermfg=84 guifg=#5fff87 “rgb=95,255,135
x085_SeaGreen1 ctermfg=85 guifg=#5fffaf “rgb=95,255,175
x086_Aquamarine1 ctermfg=86 guifg=#5fffd7 “rgb=95,255,215
x087_DarkSlateGray2 ctermfg=87 guifg=#5fffff “rgb=95,255,255
x088_DarkRed ctermfg=88 guifg=#870000 “rgb=135,0,0
x089_DeepPink4 ctermfg=89 guifg=#87005f “rgb=135,0,95
x090_DarkMagenta ctermfg=90 guifg=#870087 “rgb=135,0,135
x091_DarkMagenta ctermfg=91 guifg=#8700af “rgb=135,0,175
x092_DarkViolet ctermfg=92 guifg=#8700d7 “rgb=135,0,215
x093_Purple ctermfg=93 guifg=#8700ff “rgb=135,0,255
x094_Orange4 ctermfg=94 guifg=#875f00 “rgb=135,95,0
x095_LightPink4 ctermfg=95 guifg=#875f5f “rgb=135,95,95
x096_Plum4 ctermfg=96 guifg=#875f87 “rgb=135,95,135
x097_MediumPurple3 ctermfg=97 guifg=#875faf “rgb=135,95,175
x098_MediumPurple3 ctermfg=98 guifg=#875fd7 “rgb=135,95,215
x099_SlateBlue1 ctermfg=99 guifg=#875fff “rgb=135,95,255
x100_Yellow4 ctermfg=100 guifg=#878700 “rgb=135,135,0
x101_Wheat4 ctermfg=101 guifg=#87875f “rgb=135,135,95
x102_Grey53 ctermfg=102 guifg=#878787 “rgb=135,135,135
x103_LightSlateGrey ctermfg=103 guifg=#8787af “rgb=135,135,175
x104_MediumPurple ctermfg=104 guifg=#8787d7 “rgb=135,135,215
x105_LightSlateBlue ctermfg=105 guifg=#8787ff “rgb=135,135,255
x106_Yellow4 ctermfg=106 guifg=#87af00 “rgb=135,175,0
x107_DarkOliveGreen3 ctermfg=107 guifg=#87af5f “rgb=135,175,95
x108_DarkSeaGreen ctermfg=108 guifg=#87af87 “rgb=135,175,135
x109_LightSkyBlue3 ctermfg=109 guifg=#87afaf “rgb=135,175,175
x110_LightSkyBlue3 ctermfg=110 guifg=#87afd7 “rgb=135,175,215
x111_SkyBlue2 ctermfg=111 guifg=#87afff “rgb=135,175,255
x112_Chartreuse2 ctermfg=112 guifg=#87d700 “rgb=135,215,0
x113_DarkOliveGreen3 ctermfg=113 guifg=#87d75f “rgb=135,215,95
x114_PaleGreen3 ctermfg=114 guifg=#87d787 “rgb=135,215,135
x115_DarkSeaGreen3 ctermfg=115 guifg=#87d7af “rgb=135,215,175
x116_DarkSlateGray3 ctermfg=116 guifg=#87d7d7 “rgb=135,215,215
x117_SkyBlue1 ctermfg=117 guifg=#87d7ff “rgb=135,215,255
x118_Chartreuse1 ctermfg=118 guifg=#87ff00 “rgb=135,255,0
x119_LightGreen ctermfg=119 guifg=#87ff5f “rgb=135,255,95
x120_LightGreen ctermfg=120 guifg=#87ff87 “rgb=135,255,135
x121_PaleGreen1 ctermfg=121 guifg=#87ffaf “rgb=135,255,175
x122_Aquamarine1 ctermfg=122 guifg=#87ffd7 “rgb=135,255,215
x123_DarkSlateGray1 ctermfg=123 guifg=#87ffff “rgb=135,255,255
x124_Red3 ctermfg=124 guifg=#af0000 “rgb=175,0,0
x125_DeepPink4 ctermfg=125 guifg=#af005f “rgb=175,0,95
x126_MediumVioletRed ctermfg=126 guifg=#af0087 “rgb=175,0,135
x127_Magenta3 ctermfg=127 guifg=#af00af “rgb=175,0,175
x128_DarkViolet ctermfg=128 guifg=#af00d7 “rgb=175,0,215
x129_Purple ctermfg=129 guifg=#af00ff “rgb=175,0,255
x130_DarkOrange3 ctermfg=130 guifg=#af5f00 “rgb=175,95,0
x131_IndianRed ctermfg=131 guifg=#af5f5f “rgb=175,95,95
x132_HotPink3 ctermfg=132 guifg=#af5f87 “rgb=175,95,135
x133_MediumOrchid3 ctermfg=133 guifg=#af5faf “rgb=175,95,175
x134_MediumOrchid ctermfg=134 guifg=#af5fd7 “rgb=175,95,215
x135_MediumPurple2 ctermfg=135 guifg=#af5fff “rgb=175,95,255
x136_DarkGoldenrod ctermfg=136 guifg=#af8700 “rgb=175,135,0
x137_LightSalmon3 ctermfg=137 guifg=#af875f “rgb=175,135,95
x138_RosyBrown ctermfg=138 guifg=#af8787 “rgb=175,135,135
x139_Grey63 ctermfg=139 guifg=#af87af “rgb=175,135,175
x140_MediumPurple2 ctermfg=140 guifg=#af87d7 “rgb=175,135,215
x141_MediumPurple1 ctermfg=141 guifg=#af87ff “rgb=175,135,255
x142_Gold3 ctermfg=142 guifg=#afaf00 “rgb=175,175,0
x143_DarkKhaki ctermfg=143 guifg=#afaf5f “rgb=175,175,95
x144_NavajoWhite3 ctermfg=144 guifg=#afaf87 “rgb=175,175,135
x145_Grey69 ctermfg=145 guifg=#afafaf “rgb=175,175,175
x146_LightSteelBlue3 ctermfg=146 guifg=#afafd7 “rgb=175,175,215
x147_LightSteelBlue ctermfg=147 guifg=#afafff “rgb=175,175,255
x148_Yellow3 ctermfg=148 guifg=#afd700 “rgb=175,215,0
x149_DarkOliveGreen3 ctermfg=149 guifg=#afd75f “rgb=175,215,95
x150_DarkSeaGreen3 ctermfg=150 guifg=#afd787 “rgb=175,215,135
x151_DarkSeaGreen2 ctermfg=151 guifg=#afd7af “rgb=175,215,175
x152_LightCyan3 ctermfg=152 guifg=#afd7d7 “rgb=175,215,215
x153_LightSkyBlue1 ctermfg=153 guifg=#afd7ff “rgb=175,215,255
x154_GreenYellow ctermfg=154 guifg=#afff00 “rgb=175,255,0
x155_DarkOliveGreen2 ctermfg=155 guifg=#afff5f “rgb=175,255,95
x156_PaleGreen1 ctermfg=156 guifg=#afff87 “rgb=175,255,135
x157_DarkSeaGreen2 ctermfg=157 guifg=#afffaf “rgb=175,255,175
x158_DarkSeaGreen1 ctermfg=158 guifg=#afffd7 “rgb=175,255,215
x159_PaleTurquoise1 ctermfg=159 guifg=#afffff “rgb=175,255,255
x160_Red3 ctermfg=160 guifg=#d70000 “rgb=215,0,0
x161_DeepPink3 ctermfg=161 guifg=#d7005f “rgb=215,0,95
x162_DeepPink3 ctermfg=162 guifg=#d70087 “rgb=215,0,135
x163_Magenta3 ctermfg=163 guifg=#d700af “rgb=215,0,175
x164_Magenta3 ctermfg=164 guifg=#d700d7 “rgb=215,0,215
x165_Magenta2 ctermfg=165 guifg=#d700ff “rgb=215,0,255
x166_DarkOrange3 ctermfg=166 guifg=#d75f00 “rgb=215,95,0
x167_IndianRed ctermfg=167 guifg=#d75f5f “rgb=215,95,95
x168_HotPink3 ctermfg=168 guifg=#d75f87 “rgb=215,95,135
x169_HotPink2 ctermfg=169 guifg=#d75faf “rgb=215,95,175
x170_Orchid ctermfg=170 guifg=#d75fd7 “rgb=215,95,215
x171_MediumOrchid1 ctermfg=171 guifg=#d75fff “rgb=215,95,255
x172_Orange3 ctermfg=172 guifg=#d78700 “rgb=215,135,0
x173_LightSalmon3 ctermfg=173 guifg=#d7875f “rgb=215,135,95
x174_LightPink3 ctermfg=174 guifg=#d78787 “rgb=215,135,135
x175_Pink3 ctermfg=175 guifg=#d787af “rgb=215,135,175
x176_Plum3 ctermfg=176 guifg=#d787d7 “rgb=215,135,215
x177_Violet ctermfg=177 guifg=#d787ff “rgb=215,135,255
x178_Gold3 ctermfg=178 guifg=#d7af00 “rgb=215,175,0
x179_LightGoldenrod3 ctermfg=179 guifg=#d7af5f “rgb=215,175,95
x180_Tan ctermfg=180 guifg=#d7af87 “rgb=215,175,135
x181_MistyRose3 ctermfg=181 guifg=#d7afaf “rgb=215,175,175
x182_Thistle3 ctermfg=182 guifg=#d7afd7 “rgb=215,175,215
x183_Plum2 ctermfg=183 guifg=#d7afff “rgb=215,175,255
x184_Yellow3 ctermfg=184 guifg=#d7d700 “rgb=215,215,0
x185_Khaki3 ctermfg=185 guifg=#d7d75f “rgb=215,215,95
x186_LightGoldenrod2 ctermfg=186 guifg=#d7d787 “rgb=215,215,135
x187_LightYellow3 ctermfg=187 guifg=#d7d7af “rgb=215,215,175
x188_Grey84 ctermfg=188 guifg=#d7d7d7 “rgb=215,215,215
x189_LightSteelBlue1 ctermfg=189 guifg=#d7d7ff “rgb=215,215,255
x190_Yellow2 ctermfg=190 guifg=#d7ff00 “rgb=215,255,0
x191_DarkOliveGreen1 ctermfg=191 guifg=#d7ff5f “rgb=215,255,95
x192_DarkOliveGreen1 ctermfg=192 guifg=#d7ff87 “rgb=215,255,135
x193_DarkSeaGreen1 ctermfg=193 guifg=#d7ffaf “rgb=215,255,175
x194_Honeydew2 ctermfg=194 guifg=#d7ffd7 “rgb=215,255,215
x195_LightCyan1 ctermfg=195 guifg=#d7ffff “rgb=215,255,255
x196_Red1 ctermfg=196 guifg=#ff0000 “rgb=255,0,0
x197_DeepPink2 ctermfg=197 guifg=#ff005f “rgb=255,0,95
x198_DeepPink1 ctermfg=198 guifg=#ff0087 “rgb=255,0,135
x199_DeepPink1 ctermfg=199 guifg=#ff00af “rgb=255,0,175
x200_Magenta2 ctermfg=200 guifg=#ff00d7 “rgb=255,0,215
x201_Magenta1 ctermfg=201 guifg=#ff00ff “rgb=255,0,255
x202_OrangeRed1 ctermfg=202 guifg=#ff5f00 “rgb=255,95,0
x203_IndianRed1 ctermfg=203 guifg=#ff5f5f “rgb=255,95,95
x204_IndianRed1 ctermfg=204 guifg=#ff5f87 “rgb=255,95,135
x205_HotPink ctermfg=205 guifg=#ff5faf “rgb=255,95,175
x206_HotPink ctermfg=206 guifg=#ff5fd7 “rgb=255,95,215
x207_MediumOrchid1 ctermfg=207 guifg=#ff5fff “rgb=255,95,255
x208_DarkOrange ctermfg=208 guifg=#ff8700 “rgb=255,135,0
x209_Salmon1 ctermfg=209 guifg=#ff875f “rgb=255,135,95
x210_LightCoral ctermfg=210 guifg=#ff8787 “rgb=255,135,135
x211_PaleVioletRed1 ctermfg=211 guifg=#ff87af “rgb=255,135,175
x212_Orchid2 ctermfg=212 guifg=#ff87d7 “rgb=255,135,215
x213_Orchid1 ctermfg=213 guifg=#ff87ff “rgb=255,135,255
x214_Orange1 ctermfg=214 guifg=#ffaf00 “rgb=255,175,0
x215_SandyBrown ctermfg=215 guifg=#ffaf5f “rgb=255,175,95
x216_LightSalmon1 ctermfg=216 guifg=#ffaf87 “rgb=255,175,135
x217_LightPink1 ctermfg=217 guifg=#ffafaf “rgb=255,175,175
x218_Pink1 ctermfg=218 guifg=#ffafd7 “rgb=255,175,215
x219_Plum1 ctermfg=219 guifg=#ffafff “rgb=255,175,255
x220_Gold1 ctermfg=220 guifg=#ffd700 “rgb=255,215,0
x221_LightGoldenrod2 ctermfg=221 guifg=#ffd75f “rgb=255,215,95
x222_LightGoldenrod2 ctermfg=222 guifg=#ffd787 “rgb=255,215,135
x223_NavajoWhite1 ctermfg=223 guifg=#ffd7af “rgb=255,215,175
x224_MistyRose1 ctermfg=224 guifg=#ffd7d7 “rgb=255,215,215
x225_Thistle1 ctermfg=225 guifg=#ffd7ff “rgb=255,215,255
x226_Yellow1 ctermfg=226 guifg=#ffff00 “rgb=255,255,0
x227_LightGoldenrod1 ctermfg=227 guifg=#ffff5f “rgb=255,255,95
x228_Khaki1 ctermfg=228 guifg=#ffff87 “rgb=255,255,135
x229_Wheat1 ctermfg=229 guifg=#ffffaf “rgb=255,255,175
x230_Cornsilk1 ctermfg=230 guifg=#ffffd7 “rgb=255,255,215
x231_Grey100 ctermfg=231 guifg=#ffffff “rgb=255,255,255
x232_Grey3 ctermfg=232 guifg=#080808 “rgb=8,8,8
x233_Grey7 ctermfg=233 guifg=#121212 “rgb=18,18,18
x234_Grey11 ctermfg=234 guifg=#1c1c1c “rgb=28,28,28
x235_Grey15 ctermfg=235 guifg=#262626 “rgb=38,38,38
x236_Grey19 ctermfg=236 guifg=#303030 “rgb=48,48,48
x237_Grey23 ctermfg=237 guifg=#3a3a3a “rgb=58,58,58
x238_Grey27 ctermfg=238 guifg=#444444 “rgb=68,68,68
x239_Grey30 ctermfg=239 guifg=#4e4e4e “rgb=78,78,78
x240_Grey35 ctermfg=240 guifg=#585858 “rgb=88,88,88
x241_Grey39 ctermfg=241 guifg=#626262 “rgb=98,98,98
x242_Grey42 ctermfg=242 guifg=#6c6c6c “rgb=108,108,108
x243_Grey46 ctermfg=243 guifg=#767676 “rgb=118,118,118
x244_Grey50 ctermfg=244 guifg=#808080 “rgb=128,128,128
x245_Grey54 ctermfg=245 guifg=#8a8a8a “rgb=138,138,138
x246_Grey58 ctermfg=246 guifg=#949494 “rgb=148,148,148
x247_Grey62 ctermfg=247 guifg=#9e9e9e “rgb=158,158,158
x248_Grey66 ctermfg=248 guifg=#a8a8a8 “rgb=168,168,168
x249_Grey70 ctermfg=249 guifg=#b2b2b2 “rgb=178,178,178
x250_Grey74 ctermfg=250 guifg=#bcbcbc “rgb=188,188,188
x251_Grey78 ctermfg=251 guifg=#c6c6c6 “rgb=198,198,198
x252_Grey82 ctermfg=252 guifg=#d0d0d0 “rgb=208,208,208
x253_Grey85 ctermfg=253 guifg=#dadada “rgb=218,218,218
x254_Grey89 ctermfg=254 guifg=#e4e4e4 “rgb=228,228,228
x255_Grey93 ctermfg=255 guifg=#eeeeee “rgb=238,238,238