Disregarding 3rd party apps, Twitch chat has 4 color contrasts regarding nicks and background: light/dark mode and can have readable colors enabled/disabled in each. It would be nice for the user to be able to customize the nickname for each one of them, obviously that in the "readable colors" there would be a limitation with colors within a range or predefined.
For example, yellow nicks are beautiful in Dark Mode and the contrast is nice, but in light mode they are horrible to read and in "readable colors" mode they are very ugly in color. White and black nicks are invisible in chats similar to them, but have a very good contrast in reversed chats.