Inherit theme for overriding specific colors?

I want to use a specific theme as base and override/add some its of colors
The reason I don’t want to do it on the existing theme file is it might get updated by the custom component it belongs to and remove my changes?
How can this be done?

As it is yaml, can’t you juste import your theme file like

!include <other theme file>
...
paper-toggle-button-checked-button-color: 'var(--accent-color)'
paper-toggle-button-checked-bar-color: 'var(--accent-color)'
...

?

But maybe you’ll have warnings or errors that some are already defined … to test