CODE EXAMPLE FOR JAVASCRIPT

rgb to hex

function rgb(r, g, b){
  function toHex(a) { 
    if (a <= 0) return '00';
    else if (a >= 255) return 'FF';
    else return a.toString(16).toUpperCase();
  }
  return toHex(r) + toHex(g) + toHex(b);
}