Clouds

I wonder if what I am doing wrong with the underside of the cloud is trying to define it with darkness. Yes, it does get darker as I go toward the back, but it also definitely gets bluer. Okay, I've used a bunch of color transformations on the image in GIMP to get a better idea of what colors make up the cloud. I wasn't able to see before the wide band of mid-level gray on the side of the cloud. I think with that, I should be able to give it more of a top, side, and bottom. I'll keep using the blue and burnt umber mix that I have been using for gray (with varying amounts of white), but I think I'll also try out using a slightly lightened version of the paint I use for the sky for the darkest part. Maybe I'll lighten it with a more transparent white than I have been using. I've had so much luck with using color for depth in my tree paintings, I'd really like to be able to continue doing it, especially since what I am currently doing is only kind of working. Of course, I'd like to test this now, but I need to sleep, so I'll have to wait until tomorrow.