Redoing my Lizardmen army! Updated with MORE skinks!

Love it! The blue, purple and green go very nicely together.

 

Right now, all of them are predominantly cool colors (blues and purples), accented with warm colors (reds and oranges). I'd probably stick with that. If you only do one unit with a predominant warm color, it will feel out of place. Also, since you already have one blue unit with orange heads, another blue with red heads would be too similar.

I'd probably go with a predominant green scheme and a very light yellow (too dark and it would come across as warm). The other colors are accent colors so that won't matter as much as long as they are complimentary.