I expected it to be a no-brainer with a simple identify, but was wrong. For example, this is what an identify output of a 24-bpp JPEG looks like:
Notice the 8-bit (!) part. identify -verbose also refuses to list a nice and plain "24" anywhere... Am I overlooking something here?logo.jpg JPEG 640x480 640x480+0+0 DirectClass 8-bit 88.0859kb