Anyway, I was thinking about you pondering about some colours and started considering what could work on this map and got to experimenting.
So, if you are interested, here is my experiment:
I started out with colours closer to what you have, and tried to see what colours would compliment each other around the coast and in the image is what I came out with.
It was simple, the land layer was top in this case and the shallows layer below it and the ocean depth layer below that. And I used a cloudy brush with low opacity with each colour.
Hope this helps. Good luck with the rest.