Without question, the greatest Colts wide receiver of all-time, and perhaps one of the greatest wide receivers ever, was Marvin Harrison. However, Marvin was able to amass an impressive resume before the start of the 2000s. So, when you compare his accomplishments (791 catches, 10,439 yards) to Reggie Wayne's (668 catches, 9,339 yards), the argument for Harrison as greatest Colts wide receiver this decade is not so cut-and-dry, especially when you consider that Wayne amassed his numbers as the #2 option for most of this decade.
If you rank playoff performance ahead of overall stats, then someone like Reggie Wayne or Brandon Stokley will likely get your vote. I've included Dallas Clark in this category as well because the Colts do indeed use Clark like a wide receiver. We will not have a "Greatest Tight End" category, as Clark will likely win that vote over someone like Ken Dilger or Marcus Pollard.