I removed the Symbola font and re-installed it.
Now it works as expected in this pretest release:
The symbol is displayed, without color,
C-u c-x = shows that it is using the Symbola font.
Sorry about the trouble and thanks again.
Date: Mon, 25 Apr 2016 19:33:33 +0900
From: YAMAMOTO Mitsuharu <mituharu@math.s.chiba-u.ac.jp>
Cc: ptr.wang@gmail.com,
23362@debbugs.gnu.org
IOW, if the default setting works fine, is there some non-default
setting we should be telling users to avoid, in order to have
these
symbols displayed (albeit without colors)?
Installing some third-party monochrome emoji fonts? Unfortunately
I'm
not familiar with such fonts.
Symbola should do, and the default fontset already assigns the emoji
block to it. Are there any issues with Symbola on OS X?