Whenever I do night scenes, I pick a pale moonish color and a deeper blue color and lay those down first, the blue in the shadows, the moonish (normally a really really pale yellow or cream) in the highlights, and a mix in between. It will probably look silly the first couple stages with a blueish greenish underpainting, but I like how it ties the whole thing together and lends an overall "moonlit" feeling to it. I used this technique in this work [link] though the scanner kinda killed a lot of the color.If you have any other questions about the technique, feel free to ask! I use it a lot lol