I have this wire: , but the only difference is, mine is a light blue, but it is still 12/2 600 volts. What is the difference?

Last night I replaced a simple light fixture in my closet. It's just a glass dome with a pull switch. The new fixture (Boston Harbor) had this yellow material inside the canopy....like insulation or something. The instructions didn't mention anything about it and I left it in the fixture when...

Painted in 1990 and now our bathroom look so old and the wall is off the origianl yellow color. I have found a yellow color glass tile to match our bathroom. Please have look at the tile and give me some advice...