I just noticed this about an hour ago...

I got home from lunch today and checked under the car for any leakings.. none found.

I get back home from school.. checked again and saw a small amount of neon-greenish liquid on the ground in the front part of the car. I think its the water coolant, but I want to know how to fix this? My neighbor said something about a product called "stop leak"? Is this an expensive task to repair? Any advice would be greatly appreciated.

thank you