They will eventually. Don't go onto private property or down private roads to see them. Wonderful things happen for the polite birder. I'm about to get myself into major trouble here if I don't preface my tips for telling Trumpeter swans from Tundra swans. This doesn't always occur in the species.
Anomalies pop up all the time.
Then just go out there and take a shot at a good guess. A good friend of mine tells me that the difference between a novice and experienced birder is that the experienced birder won't say his guesses out loud. Makes him look wiser. This is rust stain from iron in the water they dabble in. Both swans are pretty much have white plumage when given the chance.