I have a set of green drawers, and sometimes I am looking for something in the green drawers which is green, but I also have a matching blue one. I grab one out of the drawers and shut it, only to find it was the blue one and it was just a trick of the light. Also, I have a black bag and I put a black hat in it. For a quarter of a year I thought I had lost the hat because I couldn't see it in the black bag.