Are they mating?

When I step out to my backyard, I tend to open the breezeway door slowly to avoid scaring the frog jumping away.

After I have observed this frog for some time, I learned that frogs in general don't like sudden movement of big objects. I guess it's their "flight instincts" when they detect such a movement as danger. However, if I move slowly close to just one foot away from it, it still doesn't care. That's how I took the snap shot of it in such a close distance.

One day, things got a little interesting! I saw another one in brownish color sitting side by side with the green one on the edge of the pond. Were they friends? Mating, anybody? The pattern of their bodies is totally identical, but their color is different. what gives?