@Marconius
Nice!
In the light color scheme, the #mainTitle paragraph in the header and the copyright text in the footer are both hard to read, a dark gray on darkBlue.

I'd remove the color from the `p` rule and replace the black color in the `body` rule with the dark gray color.
Alternately, add a second selector to the header CSS rule, `header, header p`, and do the same for `footer` so there's a paragraph color defined with greater specificity.