I'm seeing the following error via Chrome dev tools anywhere in the WP Multiste admin:
Failed to load resource: the server responded with a status of 404 (Not Found) http://fiddlersites.com/wp-admin/css/colors.css
It goes away if I turn off the Ultimate Color Scheme module of Ultimate Branding.
Side note: I don't think this occurs on the front end, when only the WP Admin bar loads. BUT that bar does not use the color scheme defined by Ultimate Color Schemes. It's the default WP dark gray.