Motion Effects on AC strings: What is white?

[Steven]

I have several 4-color AC super-strings with red, green, blue, and white strings plugged into 4 AC channels each. When a ColorWash motion event of red, green, or blue is used the appropriate string turns on. However, when a ColorWash motion event of white is used, all 4 channels are turned on. (At least that what it shows in the Preview window - I haven't wired the lights yet.)

Is there a way to make the motion event use just the white channel of a traditional "channel per color" prop?