I've recently transferred some files made on Mac OS, and containing emojis in their filename, to my Ubuntu 16.04 LTS machine.
The emojis show up in Nautilus, albeit monochromatic. Will I see them in full color if I switch to 18.04 LTS?
Yes, 18.04 supports colour emoji by default.
The Ubuntu desktop now ships with a full set of color emoji. Previously, emoji support was inconsistent and emojis appeared as black-and-white in some applications.
Just for the sake of completeness, I've made today a 18.04 LTS clean install: the emojis that looked monochromatic on 16.04 now look fully coloured. There are just some minor differences between the Apple and SVG emojis sets.