coolant color

I heard they can cause deposits of gunk (more of a slimy substance) to form in your coolant system it is a reaction between the different chemicals used might be a myth idk but that was why I was told not to ever mix them and honestly never seen any reason I will ever need to unless they stop making one or the other I keep a gallon or 2 in my truck and gallon of water in my personal vehicles I live in South GA so I can get by for a little bit without pre mixed coolant.