For the first 10% of the text field, one background color is used, while for the remaining 90%, another background color is applied.
<TextField
className={classes.root}
type="text"
placeholder="username"
variant="outlined"
style={{borderRadius:'50',
backgroundColor: "white"
}}
InputProps={{
startAdornment: (
<InputAdornment position="start">
<PersonIcon />
</InputAdornment>
)
}}
/>
The demo textfield can be found below: