Hello! The little green insects you found are aphids. I don't know what type but it doesn't really matter. They are not going to destroy or damage anything and they will be gone with the cold weather. I don't specifically understand why they would be inside a garage unless there is a plant int eh garage or they blew in from a nearby tree or plant. They feed exclusively on plants, so without that food, they will die.

I hope this helps!

Thank you! I thought that they were aphids. I did have a trash can in the garage which had garden refuse in it. I looked in and saw the same bugs so I moved the can outside and swept up...no more bugs! Thanks again.