Murphy and the Door Mat

I recently bought a colorful mat that has paw prints printed on it and says "Wipe Your Paws". I put it at the back door on the deck where Murphy, my bed dog, goes in and out frequently. But Murphy won't step on it! He jumps over or carefully steps around it when the door is opened. He used to spring straight up at the door handle when he wanted to come in. Now he doesn't, because he'd have to touch the mat to do so. I don't think dogs can see colors, and he certainly isn't being defiant of the message since he can't read (at least to my knowledge--though he likes to lie in my lap while I do). The texture is smooth so it wouldn't hurt his feet to touch it. I can't figure out what the problem is, except that it's something different.

Well, I guess we must chalk it up as one more of Murphy's delightful idiosyncrasies!