Guys... I think I know why the four attributes are Powerful, Happy Pure and Cool. These are four types of playing instruments!
A singer can sing really powerfully. Like Ran does, Happy like Kokoro, Cool like Yukina, or Pure like Aya. Kasumi is able to use all four attributes.
Same with guitars, Basses, Boards (Key/DJ) AND Drums.
The type colors given to the initials is not random. Try to corelate it to their personality and playstyle too!
Point for thought............ 🤔