Sweet mockups!
Hmm yeah, a purple tint could be interesting (to provide some better hue coverage). How about 90,85,180 for the dark blue? Should it be lighter maybe? Less saturated or more?
I noticed the little nudge helm did on the dark cyan-grey. If darker, it works better for subtle BG 'highlights', while also ramping better with the dark blue. However, I think it also shouldn't wander too far away from the grey, so I'm kinda split on that issue.
However, I did pull the grey down a bit in value, but mainly to make it less similar in value to the light sky, and bring it a bit closer to the dark cyan to improve the grey ramp overall.