I\'m using a bookmarklet that inserts a script tag into the current web page.
This script has some UI and an \"input type=submit....\" tag in it.
Taken from Mozilla Developer Center
Restoring the default property value Because CSS does not provide a "default" keyword, the only way to restore the default value of a property is to explicitly re-declare that property. Thus, particular care should be taken when writing style rules using selectors (e.g., selectors by tag name, such as p) that you may want to override with more specific rules (such as those using id or class selectors), because the original default value cannot be automatically restored. Because of the cascading nature of CSS, it is good practice to define style rules as specifically as possible to prevent styling elements that were not intended to be styled.
The only way you have is to set your own class on the button that is very explicit in its css rules: i.e
background-color:grey !important;
instead of
background:grey;