Yes, @mikeone is right. Luckily, I have 5 AquaMail licences for my family members, so as some have got the staged updated and others not, I can spot the difference. Here's what I mean.
The first is the previous version with the black background and the second is the new version with the grey one that really messes it up for me.
Isn't there a way to have it all black again?