Heres my happy aura storm cloud. a cloud with one blue bulb defualt range.  No special settings . clouds are scaled very large 500 to fit the Tapiu .clouds color is affected by sky color and sky light. so gray skys work better to get gray clouds .Bulb color and range effect the whole mix  too. cloud opacity will limit the bulbs transmitted range so you can additionally control transmition. I've used these for nebula in past renders.  png sprites on polgons make fast realistic placeable lightning too.