I often feel khaki has a wash of green in it that makes it less yellow than the yellows mentioned in the dictionary definition. It’s a muddy color, like the layer of silt under the glistening surface of a lake. I sense that same “hidden” grit and anger in Blonhaft.

And slate is touched by lots of colors. One of the wonderful things about slate is that sometimes it isn’t plain. Slate tiles can have grain and rivers of color within them that make them lively and interesting in their grayness.

I think you should describe Breanne’s eyes as slate instead of gray.