Duct tape is silver. Duct tape comes in colors and even camouflage patterns. But, really, duct tape is silver. 3M is stretching the meaning of duct tape by marketing transparent duct tape for “the end of ugly repairs.” It’s also supposed to last six times longer than normal duct tape. But, it’s “not recommended for use on flues, chimneys, mufflers or tailpipes” which I think means you shouldn’t use it on ducts. Since it isn’t silver, maybe you wouldn’t have anyway.