I had to go up close to figure it out. It turns out that the the pink surface is almost completely flush. The rich rust brown has wrinkles and pucks in which the speckles of iron filings differ in concentration.
I explained, "I don't like it as much as the pink one"
"Oh, I like them both" he said.
"You're the artist, aren't you?"
And a good laugh was had by all. I chatted with Stephen, he seems nice.