axo-light theme is based on nothing

I couldn't immediately find our light theme so I just used the mdbook light theme and made some stuff pink and orange in a way that I don't think has good contrast. We should dig up the proper definition.

Start by locating the axo-light theme and the mdBook light-theme definition, then compare the current colors with the project's proper theme definition. Confirm the intended colors and contrast requirements before updating the theme; done means axo-light is based on the proper definition rather than an improvised palette.

Written by the indexing model from the issue text.