JSFiddle - React, Tailwind, and code Playground

HTML

<h2>Iron bow palette</h2>
<div id="palette">    
</div>
<h2>GNUPLOT default PM3D palette</h2>
<div id="pm3d">
</div>

CSS

.box {
    min-width: 14px;
    max-width: 14px;
    min-height: 14px;
    max-height: 14px;
    display: inline-block;
}

JavaScript

function RGBtoCOLOR(rgb){
    return (rgb.r<16 ? '0' : '') +
           rgb.r.toString(16).toUpperCase() + 
           (rgb.g<16 ? '0' : '') + 
           rgb.g.toString(16).toUpperCase() + 
           (rgb.b<16 ? '0' : '') + 
           rgb.b.toString(16).toUpperCase() ;
}

var iron = [
{r: 0 ,g:  0 ,b:  0 },
{r: 0 ,g:  0 ,b:  36 },
{r: 0 ,g:  0 ,b:  51 },
{r: 0 ,g:  0 ,b:  66 },
{r: 0 ,g:  0 ,b:  81 },
{r: 2 ,g:  0 ,b:  90 },
{r: 4 ,g:  0 ,b:  99 },
{r: 7 ,g:  0 ,b:  106 },
{r: 11 ,g:  0 ,b:  115 },
{r: 14 ,g:  0 ,b:  119 },
{r: 20 ,g:  0 ,b:  123 },
{r: 27 ,g:  0 ,b:  128 },
{r: 33 ,g:  0 ,b:  133 },
{r: 41 ,g:  0 ,b:  137 },
{r: 48 ,g:  0 ,b:  140 },
{r: 55 ,g:  0 ,b:  143 },
{r: 61 ,g:  0 ,b:  146 },
{r: 66 ,g:  0 ,b:  149 },
{r: 72 ,g:  0 ,b:  150 },
{r: 78 ,g:  0 ,b:  151 },
{r: 84 ,g:  0 ,b:  152 },
{r: 91 ,g:  0 ,b:  153 },
{r: 97 ,g:  0 ,b:  155 },
{r: 104 ,g:  0 ,b:  155 },
{r: 110 ,g:  0 ,b:  156 },
{r: 115 ,g:  0 ,b:  157 },
{r: 122 ,g:  0 ,b:  157 },
{r: 128 ,g:  0 ,b:  157 },
{r: 134 ,g:  0 ,b:  157 },
{r: 139 ,g:  0 ,b:  157 },
{r: 146 ,g:  0 ,b:  156 },
{r: 152 ,g:  0 ,b:  155 },
{r: 157 ,g:  0 ,b:  155 },
{r: 162 ,g:  0 ,b:  155 },
{r: 167 ,g:  0 ,b:  154 },
{r: 171 ,g:  0 ,b:  153 },
{r: 175 ,g:  1 ,b:  152 },
{r: 178 ,g:  1 ,b:  151 },
{r: 182 ,g:  2 ,b:  149 },
{r: 185 ,g:  4 ,b:  149 },
{r: 188 ,g:  5 ,b:  147 },
{r: 191 ,g:  6 ,b:  146 },
{r: 193 ,g:  8 ,b:  144 },
{r: 195 ,g:  11 ,b:  142 },
{r: 198 ,g:  13 ,b:  139 },
{r: 201 ,g:  17 ,b:  135 },
{r: 203 ,g:  20 ,b:  132 },
{r: 206 ,g:  23 ,b:  127 },
{r: 208 ,g:  26 ,b:  121 },
{r: 210 ,g:  29 ,b:  116 },
{r: 212 ,g:  33 ,b:  111 },
{r: 214 ,g:  37 ,b:  103 },
{r: 217 ,g:  41 ,b:  97 },
{r: 219 ,g:  46 ,b:  89 },
{r: 221 ,g:  49 ,b:  78 },
{r: 223 ,g:  53 ,b:  66 },
{r: 224 ,g:  56 ,b:  54 },
{r: 226 ,g:  60 ,b:  42 },
{r: 228 ,g:  64 ,b:  30 },
{r: 229 ,g:  68 ,b:  25 },
{r: 231 ,g:  72 ,b:  20 },
{r: 232 ,g:  76 ,b:  16 },
{r: 234 ,g:  78 ,b:  12 },
{r: 235 ,g:  82 ,b:  10 },
{r: 236...