Can Mountain Lion's Preview.app be configured to use Lion's highlighting colours?
You can reinstall and use the version of Preview.app from Lion.

Instructions are here (start with post #8 and move forward from there)
http://forums.macrumors.com/showthread.php?t=1412516

Here are some of the salient parts, in case the link breaks. I'm just quoting text from the poster on the linked thread:


  The Lion Preview.app seems to be blacklisted in ML through the "Bundle
  version=719.25" entry in the Info.plist. So I changed it to something
  higher (760 in this case - 765 is the version-number from ML
  Preview.app). Now the app fails to start, because modifying the
  plist-file apparently broke the signing. Then I resigned it using this
  command: 

codesign --force --sign - Preview.app/Contents/MacOS/Preview



The linked post also contains a link to a downloadable version of Lion Preview that has presumably been modified as described. I have downloaded it and it works perfectly.