Thanks for pointing this out. At the moment, the nav bar and Pickaxe color are linked in the Brand Design settings, which is why you’re seeing both change together. Earlier versions of the Studio did let you adjust them separately, but that option isn’t available right now.
Here is one recent thread that talks about making Studio look better: Help with HTML for Studios
If having different colours for the nav bar and Pickaxe cards is important for your design, the best next step would be to submit this as a feature request so the team can track it. You can do that directly in the Feature Requests section of the community.
Appreciate you bringing it up - feedback like this really helps us improve.