Midnight bears a resemblance to the original Chara, but with a slightly tanner complexion, and rosier cheeks. They wear a darker purple and blue sweater, along with brown pants and boots, similar to Kk and Cameron.
While initially cast in a sympathetic light, Cameron admits at the end of the True Pacifist Route that Mid "...wasn't really the greatest person." He states that Midnight climbed Mt.Ebott for an unhappy reason, and that adds to Mid's "hatred to humanity". Midnight never told Cameron the reason that they had such hatred. He also mentions that they "laughed it off" when the two of them accidentally poisoned TNF by putting buttercups instead of cups of butter into a butterscotch pie they made for him.
At the end of the Genocide Route, Mid behaves in a polite manner, thanking Kk for guiding them. BUT, if Kk refuses to erase the world, they immediately become malevolent, despite the outward semblance of a child. Mid reveals that Kk's "Determination" and "human soul" awoke Midnight from death as soon as they fell.
The creator of the sprite (Midnight) was unaware that Kk was wearing a blue and purple sweater. She just didn't want to look to similar to Chara.