Good (working) example for controlling RGBW (including visualize feedback)

Hi,

RGBW is more and more popular. We need a good example how to control RGB+W to (for example) KNX. Including the possibility to visualize the selected (active) color (RGB + W) into (for example) a button or picture.

Can you create such an example, or update one of the existing examples? Including some documentation in the used Javascript, so installers undestand what is done in JS?

Thanks!