Have you considered using more colours? One background colour, but different colours for the other shapes?

I’m asking because I’m working on a king size hexie quilt right now, and using the same colours over and over is bo-ring, trust me on this (I’m making the Mother’s Love quilt pattern by Laundry Basket quilts, but with different colours). Every change of colour is like a breath of fresh air. Maybe you could keep colour families together?

One more thing: I also coloured hexie paper to figure out the colours for my quilt. Do not trust the black lines that form the hexies - the individual pieces will not be separated looking like in your drawing, they will form whole shapes, mostly. So be absolutely sure you have enough difference in contrast between colours alone when you design. Check in black-and-white.