You can use any dark blue as the shadow. I like Deadly Nightshade because it is slightly greeny as well. For the highlights, I try to head towards orange first and then upwards to a peach colour for the more zenithal highlights. What seems to be going wrong with yours?
Check out the articles here and elsewhere about contrast. These may help in colour choice. Also helpful would be the thread about the SM captain where the guy didn't want to hear what people said. There were loads of good links there!
David