I know the title be a little misleading. PowerApps doesn’t support CSS as of now (maybe sometime in future), but you can create a CSS light for simple tings while we await the custom Themes for PowerApps.
I find it extremely annoying when creating a large app and you need to customize visuals. If you make a change to one “screen” you have to make the same change over and over again.
In this example I declared a few variables in the beginning of the PowerApp, and one of these is the button color “RED”.
As you can see, my button color will be read when I choose to give them this color.
So at some point I decide that I want the color to be the same as my heading, and all I have to change is the color code in the app “onload”.
The result is matching buttons without having to manually change each color setting!:)
NB! after changes in the “onload”, you have to refresh the browser to see the effect.