Sorry, I thought you meant the directions form. The step-by-step route for the directions is generated and styled by Google.
MapPress does wrap the step-by-step in a div with class “mapp-dir-renderer”, though, so this may do what you want:
background-color: black !important;
color: white !important;
It might be easier to just make the directions background white (as Google was assuming it would be) so the text shows up:
If you find that you need to style individual parts of the directions, Google uses classes that begin with “adp” (“adp”, “adp-list”, “adp-fullwidth”, etc.). You can use Firebug or IE Developer tools to see how they’re being set.