Thanks for the comments, all
Basically, I think you're all right. I have complete painters block when it comes to eldar at the moment. Its the armour plates - they do my nut in. You have to do every single one of them indivudually, and they all have edges slightly less than 1mm deeep. Pain in the ass, they really are.

I can paint 7 plague marines in a week, but a squad of 6 eldar takes me about 3 weeks to do, working at the same speed. To sumamrise - it looks uninspired because it aint inspiring me
However, I want to get these guys done. Sometimes ya just gotta push through if you want to make progress, and this is one of those times.
The yellow looks dull because it is - it's a base coat of Iyanden Darksun, which is a kinda dun-yellow colour. I highlighted it by adding VMC Ivory (basically warm white), and shaded with a bit of necron abyss. I think I'll go back and re-do the armour with one more layer of Iyanden, followed by a coat of Golden Yellow. I'll then highlight this with the ivory, and shade with a dark orange like I usually do for my yellow (e.g. the yellow I did on my Ork a while back was a warm shaded yellow.)
The orange is also kinda dull because its the foundation orange. I reckon it can stay, though.
I've also redone the gun in all-wraithbone, which seems to work. The blue gems and blue gun barrel are going to be red, but I'm going to keep his eyes blue and maybe add a wee bit of freehand blue fire coming up from them over his helmet (if I can pull it off, anyway.)
I really want to keep these guys pretty simple, but they have so much detail (gemsgemsgems) on them that it's impossible to just slap some paint on em and call em done. For some reason they seem to have way more gems than even normal eldar do, and thats saying something.
Anyway, I kinda know what I'm going to do with them, but havent had a chance to make much progress on them (Sean has been a bit difficult today, and tbh I'm bloody exhausted. I crashed out for about 2 hrs this afternoon, and I usually hate sleeping during the day...)