Yes, Firefox 57 has been in the works with test versions available to all devs for a long long time. That was the period to try out a new version, not now.
Colorful tabs is now twice dead, I'll look in a few months to see if it's been resurrected.
Well https://bugzilla.mozilla.org/show_bug.cgi?id=1320585 was files long ago and we come up with solutions as and when ideas strike, not necessarily when the 57 version is forced.
