Of course there are bay duns! :) it's hard to tell from those pictures though..do you have larger ones?
-diluted body color, somewhat like that of the Creme gene (this one is a MUST-HAVE)
-dorsal stripe (this one is a MUST-HAVE)
-zebra stripes on knees and hocks
-ear lining and tips: top one-third of the ear on its back side darker than body color
-fawn color inside of ears
-mane and tail lined with lighter color (2-color mane & tail)
-cob-webbing on face
-face darker than body color
Those are some markings that dun's in general would have. Not all have/need those to be considered dun though.
Here is a website you can find helpful. http://www.mustangs4us.com/Horse%20Colors/dun.htm