The relevant WCAG1 guideline is 2.2 "Ensure that foreground and background color combinations provide sufficient contrast [...]" and this is good advice for all users, with or without impairments. Light text against a light background can be hard to read for everyone.

Try the Colour Contrast Analyser Tool [wat-c.org] to help assess whether your colours are of sufficient contrast for easy readability.

Why would you want to do this?

best quote this month ;)