Will putting green coolant in my 2021 Camry hurt the cooling system of my car?
Yes, it could sludge up and ruin your cooling system, heater etc. Green coolant is not compatible with modern stuff. Put the right coolant in your car. (consult owner's manual)
Toyota usually recommends using a certain coolant. It’s either the red or pink stuff. Toyota has their own brand, and you can pick some up at the auto parts store, look for Asian Car Coolant and make sure your car make is listed on it.
If you use the green stuff, make sure it is compatible.
If you have to use other coolant because you are in a pinch, or even plain water, they recommend draining and filling ASAP.
TL;DR - Use the Toyota recommended coolant.
It will damage your cooling system, shorten the life of the radiator. And there will be undesirable chemical reactions between the OEM fluid and the fluids with a different chemical composition. According to a recent piece, you'll increase the rate of corrosion (not good for the radiator or the engine, BTW). You could also damage the water pump. See here:
https://tap.fremontmotors.com/trusted-auto-professionals/mix-different-types-coolant
And the tens of thousands of Google hits on why it's not a good idea, besides the obvious voiding of your warranty:
