From own observation and experiments on two different installations,
Here, “supported” means both “recognise color as a valid value for type” and “having a proper visual interface” (colour well, colour picker on activation).
I was unable to get more info by googling. We might have more details on Safari 11.0.2 update in a few days on https://support.apple.com/en-us/HT201222. (EDIT: nothing interesting there.)
Also not working in Safari 11.0.3.
It works in Safari Technology Preview 52, so probably will be re-enabled in the next stable release.
Though I'm pretty sure it worked in a beta of Safari 11.1, the final released today doesn't support it. Looks like we need to wait for 11.2.
It doesn't work for me in STP 63 (Tracking Safari 12.1) or Safari 12 beta(build 13606.1.36.1.2). Did it get removed?
doesn't work on safari 12 alpha
It’s in Safari Technology Preview. It was added in v68.
Source: https://webkit.org/blog/8475/release-notes-for-safari-technology-preview-68/