Operating system and graphics card
Short description of error
Exact steps for others to reproduce the error
Make Changes to Font size and color, try to save theme and error occurs.
Based on a (as simple as possible) attached .blend file with minimum amount of steps
Steps I have taken...
Use another version of blender works fine.
Restore factory settings, restart computer, restart Blender error reoccurred.
Uninstall and remove all residual blender files preform a Clean install - error reoccurred multiple times,
Search for the error message via google, nothing relevant applied.
This error also happens when I install addons from zip files, error reoccurred when I try to activate the addon.
Thank you for your support