Hmm... maybe keep the feathers mostly black, but with a couple of stripes of color (maybe yellow and orange) near the ends of the feathers ? Ps. you might want to paint a layer of white under the colored stripes.
Look at the under tail of the one completed Saurus, the stripes don't match up xD. I've been drawing all my life, but paints are still new to me so while I have /some/ art experience it's just a medium that's pretty new to me. I can understand colour but my execution is... ehh less than I want. I'm used to more control from pencils and digital stuff. Red actually sounds like a nice idea to break up the contrast, thank you! Red and yellow with some war paint, I'm liking the idea of that already. I do have washes on these guys, however I don't think I've been doing them dark enough. They really go away once I start doing my highlighting and detail, would it be worth to put a thin wash in between crevices or just leave them as is? Hmm that's not too bad of an idea either. Or maybe a red to orange to yellow fade and black patterns on the feathers.
Honestly, from the looks of your models, I don't think that you need to change your method with washes. Washes will typically darken a model, so it's good to think two or three colors ahead of the layer you're on. This is not always the case, but is the majority of the time. Also, a red wash on red paint won't show up at all. Browns won't do very much to red either, though it does change it slightly. Just maybe not enough to notice on the table top when you have hundreds of models out. Nuln Oil will work well with red, just apply it lightly, building up to the point you want (Be careful with pooling) and then be ready to highlight and drybrush with a lighter shade of red. You obviously haven't finished your Skink Priest in the photo you posted, but for example, from the pic, I would apply a wash of Nuln Oil to the gold portion of his staff, then after that dries, I'd apply a highlight of the same gold color, then a drybrush of a much lighter gold color. That will allow it to layer appropriately and really achieve a nice depth. Personally, I like this method, though on that model, I also like a little more color on the gold portion of his staff as well, since the rest of the model has so much variation in color. One monotone color kinda distracts from the rest of the model. (You were probably going to do that anyway, but I've just seen way to many people do that with this model. ) Hope that helps!
Oof I've already painted the staff and forgot to post it, I'll pop up a current picture and ask if I should still pick up some nuln oil and put a wash over it anyway. I had been using seraphim sepia on my bronze to wash it. Oh gosh my phone does a terrible job of picking up the colours for that. Especially the metallic paint AND the blood for the blood god to decorate the skull and add colour to the staff.
He looks good, maybe just darken the claws were they meet his feet/hands and highlight the tips to add more depth (you may have done this and the camera is masking it) Lovely job
Yeah, It's a little hard to tell how the wash turned out from the photos, but if you're happy with it, then that's what matters! You can always try it out on another model and see what method you like better, and then go back and repaint the one you don't like as much. I've done that hundreds of times! The more I think about it, the more I like what n810 said about the black feathers. They would mimic the black stripes on the Skink himself, tieing the whole model together, and would also give him a dark and sinister feel, which would make him stand out against the rest of your army. Kinda like a raven. I'd give them some small blue highlights (think Batman) to give them depth. Don't go crazy with the blue though. You are doing an amazing job with blending your colors, moving from yellow to green. Keep that up! It's one of my favorite things about your work! You deserve a Spider-Man!
Calypso nice work on your Models they look really good I have just got back in to painting Lizardmen myself after a long stint of painting space marines it is really refreshing to paint bright colours for once. Regarding red washes on red paint they will work as long as the wash is a darker shade than the base red you started with if you use mephiston red as a base carroburg Crimson will work just fine as a shade as long as you don't warter it down to much I hope that helps.