You're right. Actually it came back after an update - though my Mail app & Edge have stopped working :sarc: but at least I know where to look next time it goes wrong!

Thank you very much, Soxmis, but what I was wondering was how to tell Windows to use the blue icon.

I freely admit that, in the greater scheme of crashes, re-installs and general weirdness that has been my Win10 experience to date, this is a very tiny thing. But it's annoying me. I'm using CSR...