Just because the coolant in your engine has a tinge of blue to it doesn’t mean that there’s enough antifreeze in the mix to protect the engine. Squeeze the bulb of this antifreeze tester to take a sample of your coolant and the easy-to-read scale will tell you the antifreeze content.
Better to be safe than sorry!
See the How Do I Flush and Refill My Cooling System? article in the Technical Articles section.