I also don't think it's a Colnago. Notice the cable bosses under the dowtube shifters, as if it may have originally had stem shifters. Plus the seat tube lug looks rather "thick" and as Kurt said, the seatstay caps don't look like any Colnago I've seen. However, you've already stated that it rides great, so that's what matters. And I think it looks quite nice, great color!