Can't change text color when highlighting text

Description

Setting the --on-highlight variable is supposed to set the color of the text when it's highlighted. Currently this doesn't work.

Steps to Reproduce

1. open the basic example
2. modify the css to set the --on-highlight variable to a color of your choice
3. run the example and highlight some text in the math-field
4. the text will stay the color it was and not change color when highlighted

Actual Behavior

Expected Behavior

text color should change on highlight to the set color

[Is this a regression: did it use to work in a previous version?]

Environment

MathLive version I'm on latest at the moment, or commit 9d769e03c59dd98ae07ca72de6f358eb9b31411b

Operating System [macOS, Windows, iOS. Include the version] I am using a Mac, v12.4

Browser [Safari, Chrome, IE, Firefox, etc... Try several browsers and note if there are differences between browsers. Include the version number of the browsers.] This happens in Chrome and Firefox