Styling the <option> element is highly limited. Options don't inherit the font set on the parent. In Firefox, only color and background-color can be set however in Chrome or Safari it's not possible to set any properties. You can find more details about styling in our guide to advanced form styling."
As an alternative you could try using the other single select controls like Anypicker or Autocomplete as these have options for configuring the results display (although these options don't seem to work properly for me). At the very least since they use other HTML elements to build the results list, it would be possible to write your own CSS overrides if you need custom behaviour.
For the Anypicker I was able to apply styling to the results page by overriding this CSS class