I have been able to achieve something similar using a gradient to mix between the two, and also this does give me a white floor, but this doesn't then work when its dark, so not sure of the best way with this until some kind of infinite floor is supported so it works in light or in dark. I have just tried placing a white glossy material on a plane and as long as I extend the plane enough that is working.
I'm just not sure I know which is going to be the best way to go with this, as I love it showing like when you posted "Is the idea that the letters remain black when the lights shine on them?", but I also like the ones I showed where the light colour basically takes over the logo like below.
I'm guessing this is going to have to be one or the other and just animate a mix texture from a white glossy material to a black glossy material as the lights come up. I guess that career as VFX Supervisor at ILM may be some time off yet.
And again, thank you for your help with this.
