When I think beige, I think blah. You know what’s beige? Corrugated cardboard. Manilla envelopes. Best Buy employee chinos. But what if that something beige is by Alexander McQueen? This McQueen blouse was a rare find at a consignment store. The McQueen exhibit at the Met boosted the designer’s cachet — and since his suicide, his designs are now “collectible,” with …