[Rick Osgood] wanted to build a color sensor that could be held up to any object to get RGB color values. He originally started with a photoresistor and a few LEDs, but couldn’t get that to work ...

If the color wheel above is taken as a disk on a plane ... can represent exactly the same information as a three-integer RGB value can. Every visible color is somewhere on the surface (or inside!) ...

Type an RGB or HEX value or color name into each text field ... It would be nice, however, to be able to adjust endpoint colors with a color wheel or some other mechanism when the color described ...