As far as I know, western red cedar is the only type commonly used for construction material and likewise the only cedar likely to be carried by a big box hardware store. Northern white, Atlantic white, Alaskan yellow, Port-Orford, and the eastern/southern red cedars (eastern/southern red cedar is actually a juniper, FWIW) are specialty materials not typically used for residential construction.

Redwood (Sequoia) might show up at a big box store (and may look similar to WRC) although I highly doubt it would be mislabeled as a cedar.

None the less, I'll try to describe the various cedars: Eastern/southern red cedar is generally more distinctly red in color, with white or pale streaks in the heart wood and generally a great deal of knots. Western red cedar is more reddish-brown to brown, and rarely has any pale streaks in the heart wood. It can have a lot of knots, but generally has a lot less than eastern/southern red cedar. Both have very pale to nearly white sapwood. Other cedars tend to be more pale brown to yellow to white in color. Redwood is very red (obviously!) but it can be somewhat brown and similar to WRC or eastern/southern red cedar but without the light streaks, and generally few knots. Redwood will have little if any smell, and all of the cedars will generally have a strong odor. The odor of WRC can vary, but it is a different "pencil" like smell compared to the "blanket chest" smell of eastern/southern red cedar.

Hope this helps!

: Do you know how to identify it compared to other cedar types? I asked the guy
: at Home Depot if their cedar was Western Red Cedar, and he looked at me
: like I'd asked him what the square root of a potato is.