Change border color of material ui checkbox

Here is my checkbox when checked:

Here is my checkbox when not checked:

All of the posts relating to styling the checkbox pertain to the fill color, the check color, etc. I must be missing something obvious here - just trying to make the border dark!

My code:

<Grid item xs={12}>
  <FormControlLabel control={<Checkbox onChange={(event) => {
    console.log(event.target.checked)
    setValue('isParty', false)
  }} />} label="Party" />
</Grid>