Hi, folks.
Firstly, let me apologise, especially to you, Michael, for my last contributions to political threads here. I usually keep out of those, so as to avoid posts like this afterwards. I love to read them but I'll keep my(regretably) minority political views to myself from here on, I come here for cgi, not arguments. Sorry.
So, these are just 3 local cloud spheres with just enough lighting to reach about halfway through the volumes, where direct light fails to penetrate, GI/scattering colour takes over, which is obviously here the opposite colour of the actual cloud, e.g. a red cloud has green GI(and/or scattering) contribution colour, and so on.
There is indeed some sin, and the inverse of, functions but there is no reflection or specular on the floor, Ulco. That's just pure illumination lighting from the GI, due to either excessive colour/scattering/GI/ambience levels within each of the 3 cloud volume shaders.
Cheers, all!