I dig the monochrome (black and white) version of Noto Emoji. Their announcement post mentions a few challenges they had, like:
At first the approach seemed obvious — simply redraw the Noto Emoji Color designs in black and white. They are iconic, they will be legible. Done deal. Easy peasy, lemon squeezy. Not so fast. The removal of color is no trivial task. Take for example: Flags.
I'll have to check if this can be used to replace the OS emoji. I would like to experience emojis this way, at least for a while.