How to customize button color?

Suite and Optimus Suite 6
#1

Hello,
is there a way to customize the color of a button, else than the defaults colors planned ? I tried to override the css but it didn’t work… ?

#2

CSS overriding works correctly. Example with button inside Form:
https://snippet.dhtmlx.com/mvhwx803

#3

I finally got id overriding css using the id of the button.
Thanks !