mui_component_style_override_withstyles.tsx

import { MuiAvatar } from "@material-ui/core"
import { withStyles, Theme, createStyles } from '@material-ui/core/styles'

const Avatar = withStyles((theme: Theme) =>
  createStyles({
    colorDefault: {
      // overriding `colorDefault` according to the Avatar API
      backgroundColor: theme.palette.secondary
    }
  })
)(MuiAvatar) // Passing the original Avatar component to this HOC

function myComponent() {
  return <Avatar />
}