The option was removed in latest developer 46 build.
Wow, that is an extremely unfortunate decision. It would be like if Amazon chose to ax their two day shipping option to make room for a 'new and improved' two MONTH delivery service. Giant step in the WRONG direction!
I guess I'm switching back to Firefox for now (albeit begrudgingly).
On the plus side, at least I discovered today that there actually is a way use system colors on the top bar in Firefox: http://www.askvg.com/tip-get-colored-titlebar-back-in-mozilla-firefox-in-windows-10/
^ tip: add the "tab mix plus" add-on and you can change the color of the tab text too
Thanks for Firefox