A few tips and tricks I've learned about grease guns and grease over the years:
-It's best to store grease tubes vertically. I once stored a carton of grease tubes horizontally on a shelf. I had intermittent problems with "air locking" the grease gun, especially in cool or cold weather. When I started storing the grease tubes vertically, the air-locking problem went away. My theory is that storing the tubes sideways allowed the grease to settle to the "bottom" of the tube, creating a channel of air at the top of the tube. When I jammed the tube into a grease gun and rammed the spring-loaded follower home, it captured air bubbles in the grease. Beyond that theory, I never thought about it anymore because storing the grease tubes vertically seemed to solve the problem.
-Ever buy a new grease gun and have trouble getting it to pump consistently for the first few tubes of grease? I learned from a grease gun manufacturer that it's good to smear some grease around the inside of the tube on the grease gun that holds the cartridge of grease. The coating of grease helps seal the tube against air leaks. Notice that when you pull a used grease cartridge out of an old gun, there's a "suction" that slightly resists removing the cartridge? A new grease gun won't work well until it has that coating of grease on the inside of the barrel to create similar suction.
-Aside from molybdenum grease, which is black, any coloration of grease is cosmetic. The natural color of raw grease is kind of yellowish. Blue, green or red grease is simply a marketing strategy.