why does changes.sty load pdfcolmk?
The pdfcolmk package is only useful for very old pdftex versions and does nothing in a current system. To quote the documentation
This package uses a mark register in order to solve the problem of a missing color stack of pdfTEX prior 1.40.0. Since this version of pdfTEX a color stack is available and supported by pdftex.def 2007/01/01 v0.04a. In this case this package is obsolete and the package stops its loading.
I suggest to remove \RequirePackage{pdfcolmk}
from changes.sty.