LED RGBW and ColorPicker

I'am very curious to know if someone have try to control an RGBW LED with a Color Picker approach.

i see a lot of example for RGB LED and colorpicker but how i can include a colorpicker for controlling a real RGBW LED in my project.

Any custom ''color picker'' for RGBW LED? Any sketch?

I dont need RGBW controler, i work with an arduino Uno board only and ethernet shield.

Thanks to give me somes clue or ideas about RGBW LED and ColorPicker controler (best is web based).