Blue glow You can play or use this right now (and afford it).
Gold pulse The game wants you to pick this (a target, a card to discard…).
Red 🎯 + arrow Something on the stack is aimed at this.
Orange arrow / ribbon Attacking, and who is being attacked.
Blue arrow Blocking that attacker.
Dashed outline While paying: what "Auto" would tap.
Gold / blue seat Your turn / someone else's turn. The bar in the middle shows the step.