Could you describe "sounds like he has a cold"?
I'd check (as the person above me mentioned) for any discharge (thick creamy or yellowish stuff, not watery or clear). Check to see if he's off his feed at all or generally lethargic. And check his temperature in the morning (you're going to get the most accurate reading in the morning). I'd also moniter any swelling in his lymph nodes in case it might be strangles. (we just had a few cases of that go through our barn so I'm a little hyper-sensative to strangles