Anyway, I started my army back in 2008 or so, and changed it's scheme like 6 times.
Can understand the problem with choosing it
As a general guideline, I'd say choose a color, and then check up the 2-3 main contrasts with it, if you want contrast (complementary,simultaneous(? dunno in english), opposite and quality (?))
Bright red shoots it in the atmosphere, a darkened red gives a low contrast\realistic feel, while keeping it separated.
Put in a violet, and you darken the whole model giving the evil look (that's how supervillains work, green\violet = rotting, to the human brain, not something you'd eat)
Go yellow, part of the green build (for the italian color scheme, at least), and give it a shifting feel
An so on.
To me,works nicely.
If you need to break up the models further, metallic is always an option, with bronze standing up for a contrast-wise choice. Silver\steel blends in in a more neutral way.
Last thing are washes. People seem to use them just to make gradients, but they are a nice way to low down colors, or give slight accents.
Using a x color wash on the same color base, gives it saturation (generally), making it deeper. Using the complementar (?) color, example red on green, darkens and desaturates it.
In general devlan mud (agrax something now?) works nicely to tone them all down, giving a slightly less flashy look (which i love).
Black wash is nice to cast shadows, or to turn highlights up : base, paints highlights\glazes on the edges, blackwash, repeat the highlights. they stand out a lot.
Don't know if this could be helpful, or it is clear. Hope so.
EDIT: for the scheme posted above, i've seen incubi darkness working well with it as base, hawk turquoise for the first, low highlights, and scorpion green for the edge, if you want a green-ish feel. Can't tell the new color names tho.