You are right. They wouldn't be Soapweed's cattle.
#1) they are red, as you mentioned.
#2)He would never let dogs get that close to his cattle. I know, because Soapweed, cattle and dogs have been discussed on this forum many times through the years. No cowdogs for Soapweed.
And #3) I found the source of this photo that he posted so I could share it here. I just think it is a super neat photo.