Like Hubbit said, I also use breeze dark and I never have an issue late at night!
In fact I do a lot of reviews & spend a lot of time on the forums late at night and it’s always nice and easy on my eyes.
Here’s breeze dark on the default dashboard:
Worth mentioning that breeze dark is so popular that even some of the extension devs integrate the breeze dark colours option into their extension settings!
If you’re just getting into extensions for WaniKani there are a lot of good ones that can improve your dashboard UI, here’s mine 
