Coyotes and wolfs do share some common characteristics and can look similar under certain conditions. I also feel that the expectations of the visitor often contribute to the misidentification. Wolves are usually high on the list of “to see” species in the park. Naturally, when they see an animal that “could” be a wolf they tend to identify it as such.
The most obvious difference between the species is their size, with wolves being twice as large as coyotes. Coyotes also have more pointed snouts than wolves, which tend to look more like a German Shepherd dog. Wolves can be various colors, ranging from white to black with various shades of gray the most prevalent. Coyotes tend to be yellowish to dirty brown with some shades of gray thrown in.
I have heard coyotes identified as everything from "white foxes" to "golden colored wolves". It can get pretty funny sometimes. Most of the following photos are of coyotes. One is a wolf. If you want to venture a guess which one you can post it in the “comments” section.