The general appearance of font-locking in AWK mode is much like in any other programming mode. See Faces For Font Lock.
The following faces are, however, used in a non-standard fashion in AWK mode:
NF) and “Special File Names” (such as
font-lock-warning-face. This is most noticeable when typing in a new string/regular expression into a buffer, when the warning-face serves as a continual reminder to terminate the construct.
AWK mode fontifies unterminated strings/regular expressions differently from other modes: Only the text up to the end of the line is fontified as a string (escaped newlines being handled correctly), rather than the text up to the next string quote.