Wrong top/header bar colour after opening labs

After opening labs the top/header bar colour goes dark blue. It stays that way whilst in settings, only going light again after exiting settings.

Steps to reproduce:
Go to Settings
Open labs

OS version:
iOS 14.4.2

Device:
iPhone 6s

App version:
3.75.0 #723

Screenshots:

Fine on my Android phone.

Unique to iOS?