The colour you decide on depends on whether you're coming from a UI designers point of view, a UX point of view, or an accessibility point of view, and finding the right level of all.
For example, if you were looking at 100% accessibility you'd go with black text on a yellow background and have the option to change. If you were coming from a 100% UI p.o.v. you'd probably design it to fit in with the restof the system but you might end up with something less legible. 100% UX would be well-designed enough to not make the user feel like they're looking at something which is easy to read and noticeable and probably in the correct order too.
Combine all 3 in the right ratio and you should have something which is easy to read, easy to use, looks nice and is legible to those who can't see so well.
Tip - don't RELY on colours to depict information. The colour should supplement the information, so that those who do not see colours as easily cannot get confused. So using different colours for different sections of the site, for example, without backing that colour up with text or symbols, is a nono!