It'd be great to get some screenshots of this on different types of backgrounds, with different colors of word highlight, so we can run them past lpalmaro / dmazzoni / ui review team.

Some of the STS colors look better than others against the black background with white text. Please let me know if you would like me to look at this in other areas - you mentioned different types of backgrounds.

It turns out that the screenshot feature as well as the screencastify extension doesn't respect the high contrast setting and takes the image as if high contrast were off. However, if you switch on the High Contrast mode while viewing these screenshots and video, you'll get the same experience.

This seems to indicate that the issue isn't with high contrast itself but instead that the word highlighting colors aren't a strong enough contrast in normal mode? 

Screenshots: https://drive.google.com/open?id=1Q_4TZHPKQ1qHTqcwHvklrCzCKRabOujm
Video: https://drive.google.com/file/d/1Y5PUNNzkm6Q3qaplWjFcYZoHw6EMvORh/view

STS helped me catch the typo in the title of this bug. :)

Title changed. 

Plan: Update the documentation to recommend some highlight colors over others.
Long term: Could do a smarter selection of colors when inverting.

Recommended highlight color settings for high contrast: green which is inverted to pink and pink which is inverted to green. 


Further note: the text highlight colors need to be on the fainter side because they can't conflict with being able to read the text! Even a smart inversion wouldn't change the need for translucency.  

Therefore, I feel this bug can be completely resolved with having recommended colors in documentation. Works as intended.