Setting UI Action Color

How do I set the color for UI Action buttons?
I do not see an option for it on the UI Action.

I tried Client Scripts but I see 2 problems with them:
 - They run before the page loads, so the button objects do not exist yet
 - They do not have access to DOM, document or any object in the page.

I tried this solution and variants but nothing worked.
https://servicenowguru.com/scripting/client-scripts-scripting/change-form-button-color/
I always get this error when using console.log(e) inside of catch(e){}:
TypeError: $$ is not a function