The Michelin Pilot Road rear tire has these 2 lines: 1 at the center and 1 to the left of it, that run along the whole tire. Also, they didn't mark the light spot of the tire with yellow or red paint like others...
The tiny one on the center is just mold release line as it's slightly raised. The one to the left looks like small indent that runs the whole circumference of the tire. It's only on the rear tire, not on the front.