Hi there oaklandm,
I don't actually have any Flotilla kit, but from looking at the Python API, could you not just us something along the lines of this? For instance;
brightness = module.light
if brightness > [LIGHT NUMBER]: #[LIGHT NUMBER] being the value of daylight
[Set the rainbow module to off] #If it is light, turn the rainbow module on
[Set the rainbow module to on] #If it isn't light, turn on
As far as I can tell from the example files, the module.light function gives you some sort of numerical value rather than just True or False, so that should work. In theory at least...