All users of NetSuite can customize their color scheme via the NetSuite user settings.
To do this:
Click The Home Icon in the Tool box
Click set preferences > Apperance tab
Modify the the color theme
Colors can be more than just an aesthetic change as well.
If you have a Sandbox, Development, or Release Preview account change the color scheme so you can easily discern which account you are in without having to read the account in the User Panel.