In my view Colby did win.
He has $100,000 plus an ugly-ass car. Although Tina has the Million Dollars, Colby has earned himself the title of the most honorable man on the planet.
He won almost every challenge and endeared himself to the majority. He could have written his own check for the million by voting off Keith. Instead he took the high ground, kept his word and knighted himself as the most unselfish, gratious man in America.
It is a win/win situation. The job offers, and endorsements he will get because of his actions will be 10 times the million he let slide.