Relative RGB

relative-color.js

function RGB2HEX(s) {
  return [ parseInt(s.substr(0,2), 16), parseInt(s.substr(2,2), 16), parseInt(s.substr(4,2), 16) ];
}

function ItoS(i) {
  return i === 0 ? "00" : i.toString(16);
}

function HEX2RGB(s) {
  return ItoS(s[0]) + ItoS(s[1]) + ItoS(s[2]);
}

function HexDiff(f, s) {
  return [ f[0] - s[0], f[1] - s[1], f[2] - s[2] ];
}

var metal = "000000";
var notSoMetal = "000010";
var howNotMetal = HexDiff(RGB2HEX(notSoMetal), RGB2HEX(metal));

var bob = RGB2HEX("bb00bb");
var newBob = [bob[0] + howNotMetal[0], bob[1] + howNotMetal[1], bob[2] + howNotMetal[2]];

console.log(howNotMetal, bob);
console.log(HEX2RGB(newBob));