I have this exact same problem in Windows 10. When I switch back from another user account (whether logged out or not) my Start10 menu retains the colour from the previous user.

This can be rectified by opening the personalise settings menu in Windows which resets the colour back to my colour, thereby matching all the other window borders, taskbar etc. However a permanent fix would be far preferable as it is tiresome to have to keep manually resetting the colour.

I am using the most recent version of Start10 as well as a fully up to date Windows 10. 

Any help in how to correct/fix this would be greatly appreciated.