I should let one of the real Colnago experts have at this, but based on the 1988 catalog, it's a little like the Master Piu, but with major details differing: the "crimping" of the tubes appears much more shallow than the true Gilco shaped tubes of that model, and it seems like yours only has it on the TT and DT, plus yours has no chrome on the headlugs...so must be a lower model. Seat stay treatment and forkcrown seems about right for something in the mid/late '80s...real experts will know more.
http://bulgier.net/pics/bike/Catalogs/colnago-88/13.jpg
and word to both you guys with Colnago ID questions: show the TT cable guides or internal cable routing (whichever it has).
and, I agree with vjp: dark red frame does not appear to be a Colnago.