a. Red coolant can be several types, including Asian (but not all Asian) and HD truck. The chemistries are very different and change with time.
b. The main problem with changing chemistries is NOT color. Traces of certain chemicals can interfere with certain chemistries.
c. Even more seriously, different chemistries create different passivating films. When you change chemistry, the old film and a thin layer strips away, and a new lay must be created. Mostly this is a problem for thin aluminum radiator tubes, but it something to remember every time you switch chemistries. Pick just one and stick with it. Dexcool is a common recommendation in part because it is so widely available now that the patents have expired. The original product had some problems, but it has been reformulated to resolve them.