Yes, beef soup and fat meat are deeper than chicken soup and fat meat. However, the main factor affecting the color of gravy is not fat/broth. The color of gravy is the color of gravy.
Gravy, whether brown or white, starts with broth. Flour is cooked with fat. The longer the broth is cooked, the darker the color.
Broth has four main colors, and each color is used for different applications.
Figure: Heavy diet
Cream gravy is light gravy, and brown gravy is usually deep gravy. Which flavor to use depends on the flavor you want to use. However, you can definitely use chicken oil (or bacon fat, or even shortening or butter) to make dark dough.
Once the broth turns black, both beef and chicken juice will get dark gravy. If you make exactly the same bread, with beef in one gravy and chicken in the other gravy, the nominal beef may be deeper. But they are all black gravy. Alas, if you make dark gravy, even your creamy gravy will not be as white as people who use white or golden gravy.
To be honest, their gravy is no deeper than the Turkish gravy I cooked for Thanksgiving.
Besides, it seems that they use chicken crispy skin? (The crispy part of the fried skin is very fat), these fryers may be darker than the conventional chicken oil.
TL； ? David: They don't use beef sauce. They use chicken crispy skin to make chicken juice, and may use them to make peanut butter or dark meat stuffing, which will produce dark meat juice.
Edit 1: corrected a typo.
Editor 2: Just to clarify some obvious confusion, if you click on the link in the last paragraph, you will notice that Vice at least said that KFC in Britain said that they made soup/gravy with chicken crispy skin.
I also doubt whether they are really made in China, especially in America. However, this does not mean that the factories that make the data packets they use will not use it. It's not necessarily pink.
It can be concentrated into juice (they cook the gravy so hard that the liquid must be added back to taste and consistency, which is similar to that obtained when buying chicken base).
Alternatively, they can simply send specially treated gravy bags/containers so that they can be kept for days or weeks in a process similar to canning. I don't think this is the same as canned food.
I used to work in a small chain store in Italy, and I did make my own slow cooking sauce. But this is not done in a restaurant. The factory makes it according to their formula, then puts it into these big bags, and after special treatment, the sauce can be preserved for a week or more (I don't remember how long, but I know that managers can only order one week at a time. Although there is some room for manoeuvre to prevent too many orders in a week, as far as I know, this requirement is based on economics, not corruption. The team manager who has been to the factory said that we taste it with the taste of the factory, which is really a taste.