[dom0]

Over network? Needs a networking stack in memtest.

Over serial? Physical serial is rare. SOL would work, but since it is connection-based you can't poll it.

This seems like a simple and reliable method to me.

[sschueller]

Since they take a screenshot of the console they could output a qr code and read that.

[dom0]

Patching the font colours are probably a few lines of diff, adding a QR code to a text-mode display... way more complicated.

[fapjacks]

That's sort of what they're doing. It's just a two-bit QR code: Red, and Not Red.

[gumoro]

So, one bit ;)

[fapjacks]

Hah! Yes, totally. Haha I wonder why I said that?

[BraveNewCurency]

There is also a "not decided yet" state. Hence, you were right, it needs two bits. :)