Hello David,
Could you experiment a bit in Cuelux with the values of Colour fix (ch5) and Colour scroll (ch11) in combination with the RGBW mix?
For example set some values to the R,G,B,W channels and select the last colour (#21, the RGBW square) in colour fix. Now play a bit with the colour scroll fader (SCRL). Do the same for colour #13 & #14