My friend taught me this trick the other day. She said, “First look at everything red in the room. Now look at everything blue.”
I realized two things: First, I had no explicit consciousness of either color before she drew my attention to them. When I first walked into the room where we were talking I conceptualized everything into objects like “chair” and “computer” and barely noticed the colors.
Second, when I was looking at the red, I wasn’t thinking of anything else. And when I was looking at the blue, I couldn’t think of the red. She told me to imagine as if the blue were positive thoughts and the red were negative thoughts. I had complete control to fill my consciousness with one or the other.