I've had a bit more of a think about the color scheme for the Eldar.
I think the original scheme was a step in the right direction, but not enough. Still too much colour for fighters actually trying to survive combat.
Here is the revised Guardian (you probably won't notice too many changes)
And the revised Dire Avenger. There are many changes here.
I'm still not 100% on this, so we'll see how it goes...