I'm unsure which cloud mesh you're talking about, but I have found two different clouds (they are direct downloads).
Clouds by IngredientGlave's Heavenly StuffAs you said getting it to react with light, the only thing I can think of is messing around with the ambient within the material file.
Here is a reference as to what ambient does and how it behaves. You could probably make them glow during the nighttime, but I am not entirely sure what colors you'd use. You can see the tutorial
here. You follow the same procedure and insert the coding in the material file, just like with presets.
I hope I helped you! ^_^ Please let me know if anything works or doesn't.