The color of universal antifreeze is green.
Green antifreeze can be mixed safely with most other colors of antifreeze as it's universal and is made of the correct chemicals to blend in with each other.
Water was first used before antifreeze was invented and used.
Cars could use water as coolant which was okay in warm weather but in cold weather the water would freeze in the cars radiator and engine and crack the radiator as well as the engine.
So eventually even before the antifreeze and coolant we use today they used Glycerol.
But later on the current antifreeze we use now as coolant in our vehicles is ethylene glycol.
The ethylene glycol antifreeze we still use today does still contain some water so that the coolant does not freeze as if the ethylene glycol was put straight into the vehicle without a mixture of water then it could still freeze.
So it's important to mix water with straight antifreeze.
However if you have 50/50 premixed antifreeze then no water should be added.