Color Deilema

Alright, here's the situation. I'm painting a squad of Alpha Legionnaires right. Well, I'm leaning towards a odd blue/green/purple hue like that on the cover of the HH book Legion. I'm pretty happy with the armour color at the moment. Looks a big greener/purplier IRL that this picture btw. However, I can't decide on what would be a suitable color for their cloaks. I tested straight purple on one and it looked horrid. Doubt even darkening it with badab black wash would help either....
Not quite sure what color to go with. Perhaps a dark green like Dark Angels green. Thats about the darkest I have anyways. Hmmm....

*UPDATE*

Tried experimenting with green and here's what I got.
One person on the BoLS forum suggested trying a blend of red, however that adds a worry of xmas tree syndrome. This however might cover the model in too many like colors.... Very difficult. I do like this green cloak though.