Problem Color Printing From Mobile Version

When I attempt to print a task list from the mobile version of GTDNext using my iPhone, the list displays on my screen in color but prints only in black and white. Yet when I log out and return to the GTDNext main website, that page prints in color.

This behavior is reproducible in both Chrome and Safari. iPhone 5 running iOS 9.1. Printing to a Cannon MG6320 color inkjet via AirPrint. I have rebooted the phone and the problem persists.

Is it possible there is something happening on my project page that is preventing color printing? Any help or suggestions for testing appreciated.