I'm pretty sure the yellow colour for emoji was chosen by NTT in Japan
Starting my online life in FIDO, with its deep and reach culture of text smiles (a hundreds of them were invented and tens of them were in wide circulation) I was personally offended by these stupid yellow circles.
What I don't like is when software/services try to be 'clever' / 'helpful' and 'translate' ASCII smileys into emojis. At this point I have to `backtick` sometimes to keep them as-is.