Hi Tim,
The WeBWorK install script that Jason Aubrey wrote
https://github.com/aubreyja/ww_install
mentions that chromatic needs to be installed for the NAU graph theory problems to work. My hunch is that if you install chromatic, your error messages will go away. Here is the relevant excerpt from the README.md file:
#############
Other files
The extra/ subdirectory contains scripts which help with optional post install tasks. These are not currently hooked into the other scripts, so you'll need to run them separately. Currently contains
install_chromatic.pl
Standalone script to compile pg/lib/chromatic/color.c so the NAU library graph theory problems work. This functionality has been incorporated into ww_install.pl, so it should not be necessary to run this script. However, if you find the NAU graph theory problems are complaining thatpg/lib/chromatic/color doesn't exist, then you can run this script to compile it for you.
######################
You may also need to restart the apache server or webwork (or both) after installing chromatic. (I'm not sure about this, but restarting couldn't hurt.)
Best regards,
Paul Pearson