Unlit view - colours different between UE4 and UE5

Has something changed to do with colors / colorspace between 4.27 and 5?

I upgraded a project to UE5 and the same scene looks slightly different in unlit mode between engines. In UE4 it looks a little ‘flatter’.

In particular I’m comparing the unlit colour of a sphere with the M_GreyBall material (used for colour correction). UE5 has more colour variation, and I’ve verified this with an eyedropper app.

My guess is either a change to default colorspace, or the way that unlit mode works