Printing is not my bag. Just trying to get enough info going so someone more used to printing knows where to jump in.
I did discover that 1512 just doesn't do color calibration. Its data files come with the correct settings, and as hinted by your cross-post, those data files only come with later versions of hplip. There is a way to set the parameters manually, but that's beyond my knowledge.
It's possible to try hplip.SlackBuild from 7.2 on 7.0. Don't know how the dependencies would sort out. I'm out of time right now. If you want to try a build, remind me by posting back and if someone doesn't get to it before I can, I'll offer some tips on that.
If you want to read ahead, the 7.2 hplip.SlackBuild and other needed files can be retrieved with
for i in hplip.SlackBuild doinst.sh slack-descIt's probably better to be a regular user than doing this part as root. Be sure you're already in the directory where you want the files to go. And doing chmod +x hplip.SlackBuild isn't absolutely required, but may make things easier if you do run the SlackBuild. For actually running ./hplip.SlackBuild you do have to be root.
wget -c --no-check-certificate -O ./$i https://bitbucket.org/VLCore/vl72/raw/HEAD/var/vabs/hplip/src/$i