The blue lines are chalk. I also found out that this is an Armstrong Intergrid suspension ceiling.
I got these yesterday at Gordman's for $3 each. I'm going to use them to cover 3 small holes in the wall in the laundry room.
More dining room pictures to come...James should have the light out and the chandelier up tonight. Then tomorrow I get to take out the frame and the paneling. And then comes the agonizing process of picking out paint. I hate picking paint...I want color, James wants off white, so I have to find something that makes us both happy.