Meaning
A solid yellow circle, one of the coloured circles from emoji version 12.0. It means yellow and often signals caution, waiting or an away status.
It fits traffic-light style updates, colour-coded calendars and anything yellow, from the sun to a lemon or a ripe mango: “Me right now: 🟡 online but busy” Some use it as a tiny sun in minimalist posts. For a yellow square, as in sports cards or word-game grids, 🟨 is the match.