react-test/docs/data/material/components/text-fields/CustomizedInputsStyleOverrides.tsx

import TextField from '@mui/material/TextField';
import { outlinedInputClasses } from '@mui/material/OutlinedInput';
import Box from '@mui/material/Box';
import { createTheme, ThemeProvider, Theme, useTheme } from '@mui/material/styles';

const customTheme = (outerTheme: Theme) =>
  createTheme({
    palette: {
      mode: outerTheme.palette.mode,
    },
    components: {
      MuiTextField: {
        styleOverrides: {
          root: {
            '--TextField-brandBorderColor': '#E0E3E7',
            '--TextField-brandBorderHoverColor': '#B2BAC2',
            '--TextField-brandBorderFocusedColor': '#6F7E8C',
            '& label.Mui-focused': {
              color: 'var(--TextField-brandBorderFocusedColor)',
            },
          },
        },
      },
      MuiOutlinedInput: {
        styleOverrides: {
          notchedOutline: {
            borderColor: 'var(--TextField-brandBorderColor)',
          },
          root: {
            [`&:hover .${outlinedInputClasses.notchedOutline}`]: {
              borderColor: 'var(--TextField-brandBorderHoverColor)',
            },
            [`&.Mui-focused .${outlinedInputClasses.notchedOutline}`]: {
              borderColor: 'var(--TextField-brandBorderFocusedColor)',
            },
          },
        },
      },
      MuiFilledInput: {
        styleOverrides: {
          root: {
            '&::before, &::after': {
              borderBottom: '2px solid var(--TextField-brandBorderColor)',
            },
            '&:hover:not(.Mui-disabled, .Mui-error):before': {
              borderBottom: '2px solid var(--TextField-brandBorderHoverColor)',
            },
            '&.Mui-focused:after': {
              borderBottom: '2px solid var(--TextField-brandBorderFocusedColor)',
            },
          },
        },
      },
      MuiInput: {
        styleOverrides: {
          root: {
            '&::before': {
              borderBottom: '2px solid var(--TextField-brandBorderColor)',
            },
            '&:hover:not(.Mui-disabled, .Mui-error):before': {
              borderBottom: '2px solid var(--TextField-brandBorderHoverColor)',
            },
            '&.Mui-focused:after': {
              borderBottom: '2px solid var(--TextField-brandBorderFocusedColor)',
            },
          },
        },
      },
    },
  });

export default function CustomizedInputsStyleOverrides() {
  const outerTheme = useTheme();

  return (
    <Box
      sx={{ display: 'grid', gridTemplateColumns: { sm: '1fr 1fr 1fr' }, gap: 2 }}
    >
      <ThemeProvider theme={customTheme(outerTheme)}>
        <TextField label="Outlined" />
        <TextField label="Filled" variant="filled" />
        <TextField label="Standard" variant="standard" />
      </ThemeProvider>
    </Box>
  );
}