Color schemes

The color you choose for your UI will play an important role in not just its visual appeal, but in the player's interpretation of what the UI does. The colors of the UI should stand out compared to the background, but it should also not stand out so much that it causes eye strain. There is no specific color scheme you have to use for your game, but as a general rule, split complementary color schemes are the best for reducing eye strain while also producing enough contrast to make items distinguishable.

Whenever possible, you should also avoid color combinations that will be indistinguishable to those who are color blind; if it's not possible, use other indicators to make items distinct.