How to change the background-color of a button?

Question

css

Hello!
Guys, tell me please, otherwise it’s too late and my head doesn’t want to cook at all ...
The crux of the matter:
There is a standard bootstrap menu, there is a button (here it is :) that is responsible for showing and hiding the menu. When pressed, the menu pops up, and this button has a dark background, like this:
But when I hide the menu, this dark background remains.
Can you please tell me how to remove it when the menu is hidden again? And then it somehow does not look aesthetically pleasing ...
Thank you in advance!

Answer 1

Try
:focus {
background:...
}