The javadoc command to generate the main API docs includes this option, which contains $(HASH), which should probably be substituted:

-top '<div style="background-color: $(HASH)EEEEEE"><div style="padding: 6px; margin-top: 2px; margin-bottom: 6px; margin-left: 6px; margin-right: 6px; text-align: justify; font-size: 80%; font-family: Helvetica, Arial, sans-serif; font-weight: normal;">Please note that the specifications and other information contained herein are not final and are subject to change. The information is being made available to you solely for purpose of evaluation.</div></div>'