Mui:Button

import {createTheme, styled, ThemeProvider} from '@mui/material/styles';
import grey from '@mui/material/colors/grey';

const greyTheme = createTheme({
  palette: {
    secondary: {
      main: grey[700],
    },
  },
});

// ...

return (
  <ThemeProvider theme={greyTheme}>
    <Button sx={{marginLeft: 1}} color="secondary" variant="outlined">Label</Button>
  </ThemeProvider>
);