User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:57.0) Gecko/20100101 Firefox/57.0 Build ID: 20171112125346 Steps to reproduce: 1. Open Firefox 2. Open dev console, enable requests / XHR 3. Fetch a page that returns non-success HTTP 4. Look at console Actual results: New (failed) requests is show in default (blue) color Expected results: New request is shown in RED color (at least the right side "HTTP/1.1 Internal Server Error"). Alternatively, it could have a red background as console.error messages It was like that in previous Firefox version, before you changed color schema. What we need is a good color indication, so we could identify errors quickly.

Hello Artem, thanks for filing a bug. We introduced colors in Bug 1417805, so i'm marking this one as duplicate.

The changes landed in Nightly yesterday, so it will be in Firefox 59 :)