Hello Ciarra,
I've repaired Office per step 1, which finished successfully.
I don't believe uninstalling and reinstalling is necessary, as PowerPoint performs perfectly outside of this one small problem.
The other steps in your list pertain to Word which this issue is not connected to.
I've noticed a few odd things here which I would like to show some pictures of. Please refer to the hyperlinks again.
I'll use this slide section as an example in case my original post wasn't clear.
1.) If I try to make this intended change, save the file and then reopen it, I get this result.
2.) I can color the entire equation, save the project, and reopen it with persisting changes.
3.) I can color every denominator, save the project, and reopen it with persisting changes.
4.) If I color the 1 digit in the numerator and the following units, only some changes persist upon reopening.
Notice that it failed to save the coloring of the 1 digit in the 2nd ratio on the left-hand side of the equation.
This seems to suggest that there may be some sort of font color bug related to specific instances of the equation feature in PowerPoint.
The issue can be reproduced 100% of the times I attempt it, and I can copy of the file for further investigation if needed.
For now, I'm able to get around the issue by doing these steps:
With this workaround, the changes persist upon saving and reopening. Not exactly an optimal solution. Hopefully this makes sense.