Comment 6 for bug 1419565

Indeed, high-contrast, any much of the boot settings on the server iso (and apparently alternate images) appear to not work properly. Reassigning this to gfxboot-theme-ubuntu; which seems like it's more likely to be the package at fault: if one edits the command line manually to add the right options, they are properly taken and used.

Of note; the desktop image seems to work just fine.