Great scratchs !! You really should post one of those "how to"s in the article section, you know...Guess the Red Rams had a different tone of red to differentiate 'em from Blood Angels. But to really prevent "over-dull", you might try a few decals or letterings (white or yellow), you know, a DANGER sign here and there, the contrast will make the vehicle stand out.
An ambitious diorama, but a little sterile and lifeless - there should be more vegetation & rocks, and the ground shouldn't be so flat. The armour and figures are well done.