NDP - How about Nice Drain Plug? Reds are hot water, blues are cold water. As I stated earlier, remove these fittings and put ball valves on for easier draining and winterizing.
For safety sake, when you are trying to take the caps off, make sure your water pump is turned off as well as your hot water heater. Open your faucets to relieve any pressure. Then you may proceed with trying to take the caps off. I have the same style caps on mine for low point faucet drains. I replaced them with 1/4 turn ball valve to make draining and winterizing simpler.
Dang, I'm repeating myself. Don't tell my wife, she has to tell me things 10 times.