First paste a color wheel onto a drawing canvas object. Then use the save snapshot action. Afterwards you can use the snapshot(rgba)at(x,y) expressions to get the color from any given pixel in number form, and do whatever you want with it.
Return the red, green, blue and alpha components of a pixel in a saved snapshot. The position is given in pixel co-ordinates, and the returned value is returned in the 0-100 range. For more information see the section Pixel manipulation with snapshots above.