Font Lock mode can highlight using any face, but Emacs defines several faces specifically for Font Lock to use to highlight text. These Font Lock faces are listed below. They can also be used by major modes for syntactic highlighting outside of Font Lock mode (see Major Mode Conventions).
Each of these symbols is both a face name, and a variable whose default value is the symbol itself. Thus, the default value of font-lock-comment-face is font-lock-comment-face.
The faces are listed with descriptions of their typical usage, and in order of greater to lesser prominence. If a mode’s syntactic categories do not fit well with the usage descriptions, the faces can be assigned using the ordering as a guide.
for a construct that is peculiar, or that greatly changes the meaning of other text, like ‘;;;###autoload’ in Emacs Lisp and ‘#error’ in C.
for the name of a function being defined or declared.
for the name of a variable being defined or declared.
for a keyword with special syntactic significance, like ‘for’ and ‘if’ in C.
for comments delimiters, like ‘/*’ and ‘*/’ in C. On most terminals, this inherits from font-lock-comment-face.
for the names of user-defined data types.
for the names of constants, like ‘NULL’ in C.
for the names of built-in functions.
for preprocessor commands. This inherits, by default, from font-lock-builtin-face.
for string constants.
for documentation strings in the code. This inherits, by default, from font-lock-string-face.
for easily-overlooked negation characters.