If you want to know what Kai,Addison and Harue are based off of…well…
Kai,Harue and even partially Addison are based off Yin and Yang…Kai is Yin,Harue is Yang and Addison is both or the main Yin and Yang symbol,representing balance…and their designs also reflect this…with the splotches of black and white on Kai and Harue respectively…and with Addison having the front of her hair being half black half white. Also…Harue’s dark hair with her favourite colour being pink,a very soft colour is a contrast to how she’s an utter meanie but is sweet when you don’t see her bad side. And Kai’s light blue hair but with his favourite colour being black with a bit of darker orange is also a contrast to how he’s a really kind person,but looks like an emo boy that is closed off. Addison’s colour pallet is both black and white with green. Green being classified to some as a neutral colour,ultimately fits to Addison’s role of being both Yin and Yang,or the symbol of it,or in my case,the balance. I hope this explains their designs a bit.
[Sorry for the long paragraph-]