This is what I did for our large painting in our water colour unit.
I did a wet on wet wash of purple and blue in the background. Once that was dry I penciled in the fairy.
For the spider web I used really washed out purple and put some salt on it while it was still wet to give it a rain slicked spider web look. For the rain drops, I put dabs of purple and blue on the paper, then I put water dabs on top of the paint and blew it in the direction I wanted it to trail. I think that ended up having a very neat effect.
Then I got to work on the fairy. I used a lot of gridation on the wings, and just solid colour blocks of blue and purple.
Throughout the entire composition I used the same three colours, purple, blue, and a mixture of the two that added a darker tone.
I erased the pencil marks after the paint had dried.
I was very pleased with the way this turned out. And was happy that I got a good mark on it.