How to prevent TOC font from changing color? (RH 2020)

Hi, Everyone.

In RH 2020.4.173, I'm trying to set the color of the main TOC to black and only black. I've changed the font color in the skin editor. But the TOC behavior remains unchanged -- it starts out all black. But when I click on some topics, the whole TOC changes to purple (with the selected topic blue). Clicking some topics changes it all back to black. But others, purple.

Each topic that changes from purple to black will do so consistently. However, I cannot detect a pattern that explains why certain topics go purple while others go black. 

Is there a setting where I can just disable the color change, globally? That's what I really want. User testing tells us the color changes are annoying and distracting. Our end user tries to understand what the color changes represent. But it becomes clear the color changes aren't systematic.

Thank you!