Is there any way to change the white background theme in the email app and gmail app

So I downloaded one of the free Black themes from Samsung store and loved how it changed the background of the Message App, Calendar App, Phone and even the Settings App to nice deep black. But my Gmail and Email apps are blinding white. Is there any dark theme that works on these two offenders?

Also I tried some slick black icons but noticed that when installed the Calendar Icon doesn't display the correct date. I use Nova launcher so perhaps that is the reason why that icon won't work?