In Boost, I change my background colors with the css code shown below. I can't say that this is the best css, but it works for me. You might want to experiment with it a little before settling upon your final solution.
/* Change the color scheme and some spacing for manually grading quiz questions.
This matches the old MORE theme color scheme. */
.alert-info, #page-admin-index .releasenoteslink, #adminsettings .form-overridden, .que .formulation {
background-color: #d9edf7;
border-color: black;
color: black;
}
.alert-warning, #page-admin-index .adminwarning, .uninstalldeleteconfirmexternal, .que .outcome, .que .comment {
background-color: #dff0d8;
border-color: black;
color: black;
}
.que.essay .qtype_essay_response {
padding: .25em;
}