Go with a color component of the main color, i.e. one of the colors mixed to make that plum. Which is why I chose a dark blue. Head tube and panel on the seat tube. The brain understands this. White lettering and don’t worry about vertical lettering, it will look fine. Polished components will set off the dark blue, or vice versa....
Trust me. Or not. Giving advice I don’t have to live with is easy.