Crazy mixed-up moth

These warm days, the coffee shop where we refuel after walking on the beach keeps all its doors wide open, to catch the breeze. Last Sunday, this moth flew in and settled on the floor near our table.

I think it's a geometrid, a measuring worm moth.

It's a pretty moth, hardly tattered at all yet; a youngster. And do you see what's odd about it? I was so concentrated on getting it all in focus that I didn't even notice until Laurie pointed it out at home.

The wings on the left side are mostly brown, with black designs. On the right, they're mostly grey, with brown accents. And if you look at the thorax, it's also split down the middle. Here, the right is mostly grey, and the left is brown.

Thorax, collar, and upper wing.

I thought it was an effect of the light, but in all my photos, from whatever angle, it's the same. And the lighting was uniform; the shadow falls evenly underneath the moth. Wonky genes?

I've sent it in to BugGuide for an ID.
UPDATE: Triphosa haesitata, a Tissue moth (one of the Geometrids). BugGuide is wonderful!