Is it possible to create a material ui theme using css?

Question

Using material-ui for react, theming is possible using JSS. eg.

import { createMuiTheme } from '@material-ui/core/styles';

const theme = createMuiTheme({
  palette: {
    primary: {      
      main: 'red',
      light: 'pink'
      ...

Is it possible to set the color variations using css? eg.

.SomeSelectorForAllClasses {
   --primary:'red';
   --primary-light:'pink'
...
}