My main laptop uses Outlook 2007, with a pale blue background scheme. Much like the very much missed Outlook Express which I used to have before Micro$oft killed it off.
But the back up laptop uses Office 365 with Outlook 2016. Much inferior, with 'white', 'dirty white' and 'a bit grey' as the only colours available. Perhaps because that makes it easier on kiddies' iToys and tablets?
I find Outlook 2016 a real backward step. Absurdly complicated if you have more than one e-mail account and that horrid white background. I do hope that the 'blue' background is reintroduced - M$ won't admit it, but they've had hundreds of complaints.