How to change Material UI input underline colour?

Question

I have a Material UI Select component that is on a dark background, so for just this one component I\'d like to change it so that the text and line colours are

Answer 1

If the goal is simply to turn the underline (and text as well), there's a very simple solution, which also works with many other components (, , etc.):

const theme = createMuiTheme({
    palette: {
      type: 'dark',
    },
  });

It will catch the underline and turn it white.

For details on what this will change, in case you want to override elements of it: https://material-ui.com/customization/palette/#dark-mode

(If you've never used a theme before, you'll need to import createMuiTheme and wrap your component in it; see https://material-ui.com/customization/theming/)