While working on Rave Cage Carnage at Tonkotsu Games, I was responsible for Game Design, as well as UI Design. The core focus of this design was clarity, bold shapes (super straight, square backgrounds as panels), as well as identification by colors.
The darkest colors should always be the background, commonly in a very dark grey-tone. Selected elements (most commonly elements) and dynamic panels are outlined with a thick white outline. On top of that, white is generally the color of interactive elements. Additionally, some surfaces have colors on them, such as buttons whch are representative of outfit colors (visible in the Shop UI) or buttons based on enemy types (here in blue due to the enemy type in the Library UI). I also worked on a mobile version of this UI.