How to change face in particular theme locally?

Question

The title says it all. How to change face in specific color theme locally, in my configuration?

Answer 1

Use custom-theme-set-faces in a with-eval-after-load to easily customize a theme.

For example, this modifies ample-theme to have a lighter background and green keywords instead of the defaults.

(with-eval-after-load "ample-theme"
  (custom-theme-set-faces
   'ample
   '(default ((t (:foreground "#bdbdb3" :background "gray15"))))
   '(font-lock-keyword-face ((t (:foreground "#818053"))))))