Can't get Skylight colour to change at runtime

So I have 2 different zones I can walk between, and I need to blend things like skydome/fog/directional light and skylight. The skylight is proving to be tricky. If I set the skylight to have a Lower Hemisphere colour, and try to tell it to change in the blueprint, it does nothing.

Is it possible to change the lower hemisphere skylight colour at runtime please?