I'm glad you posted a screen dump, as without it I'd be describing how to use the "Change Appearance" CSS facility.
It's not the text colour that is the problem but the background image. It has far too much contrast. You'll never find a text colour that will cope with a background that changes from near white to near black.
Change your image to make the light areas darker or the dark areas lighter, only then should you chose a colour for the text.
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.