This is the official manual for the latest Org-mode release.
Org mode highlights TODO keywords with special faces:
for keywords indicating that an item still has to be acted upon, and
org-done for keywords indicating that an item is finished. If
you are using more than 2 different states, you might want to use
special faces for some of them. This can be done using the option
org-todo-keyword-faces. For example:
(setq org-todo-keyword-faces '(("TODO" . org-warning) ("STARTED" . "yellow") ("CANCELED" . (:foreground "blue" :weight bold))))
While using a list with face properties as shown for CANCELED should
work, this does not always seem to be the case. If necessary, define a
special face and use that. A string is interpreted as a color. The option
org-faces-easy-properties determines if that color is interpreted as a
foreground or a background color.