Ubuntu 20.04.3

Pharo-9.0.0+build.1573

I am a noob just getting started with Pharo.

After tuning some System preferences (e.g. switching to Pharo Light theme, etc.) the lessons in ���Learn Pharo��� available from the ���Welcome��� window are near black and unreadable.

When I click on ���Learn Pharo��� the initial page is okay (black or blue type on a black background) but doing ���ProfStef go.��� messages opens the next lesson where all text has such a black background it is unreadable. Doing ���ProfStef next.��� or ���ProfStef previous.��� on subsequent pages opens a new page similarly illegible.

I���ve searched through all the System prefs but can���t figure out which one affects the lesson pages.

Regards, Hedley