I'm lucky I guess that I get to play with thermal optics at work (the old night vision sights didn't work for squat passed about 300yds). Even now, as I can make out four-legged animals at close to twice the range you want, there isn't enough available image to make it enjoyable for a hobbiest. The color is still green for us, just as it would be with regular night vision. The downside is that when you are looking at crap in the desert heat, the sights have a tendency to wash out.
The infared cameras that we had last time I was in country could go out well passed that even, but you are looking at either an all black/white silohuette.
Cheap idea...get a trail cam.