Another update that should be useful for Commander players: I have just added a color identity check to our deck legality checker! It will now find your Commander, figure out its color identity, and then check all cards in your deck to make sure they conform to it. If there are any problems, you will get a message telling you what's wrong.
I have also updated the way that legality problems are displayed in decks. In addition to the list of problems at the bottom it will now also show
warning icons next to the relevant cards, making them easier to find.
Since this is a new feature, please double-check any legality messages you see over the next few days. As usual, please get in touch here, on Discord or on Twitter if you notice anything wrong.