code: function rgb2html(r, g, b){
      if(r.length) { b = r[2], g = r[1], r = r[0]; }
      var s = '#' +
        Number(0x1000000+r*255*0x10000+g*255*0x100+b*255).toString(16).substring(1);
      return s;
  }
docs: Converts RGB color value to HTML5 color value (string)
  Conversion forumla:
  - convert R, G, B into HEX strings
  - return HTML formatted string "#RRGGBB"