[Solved]-Material UI Toggle Button - can't change background color when selected-Reactjs

Try that in your global css or scss file:

button.MuiToggleButton-root.Mui-selected {
  background-color: #1f792f !important;
  border-color: #000 !important;
}

Create new class and dont forget to use !important to override the backgroundColor of "Mui-selected" class

classes= useStyle({
newClass { backgroundColor:'red!important'},
})

<ToggleButton 
classes={{ 
selected:clasess.newClass,
.
.
.
}}
value=''
/>

  const useStyles = makeStyles(theme => ({
    ToggleButton : {
        '&.MuiToggleButton-root.Mui-selected': {
            backgroundColor: theme.palette.common.white,
        }
    }
}));