Trouble with font colour on toolbar tabs

When I view the toolbars of LO 6.2 by tabs (a la MS Word), all the text and background changes to white or very light grey. So I can’t see the text!

I’ve tried:
Changing the theme

Changing the icon theme

Changing the font colour through tools > options > advanced > expert configuaration > search:personasettings > misc > change #rrggbb value.

Retarting LO.

Any other ideas?

(I wonder if there’s some bug with text colour, because all my tracked changes and hyperlinks are the same colour as the rest of the font despite my specifying otherwise.)