I use the "Classic" scheme (available from the drop down list at the bottom left of the page), so I don't have this problem.

Looks like there is some problem with how the schemes are implemented - at the moment, I am typing Black text on a White background, but you will see it as White text on a Grey background. However, when I use Navy text on a White background, it is rendered to you as Navy text on a Grey background which is not, as you mention, an especially easy combination to read!