The wall that was not white

An original account of an invented painting lesson.

I painted the wall behind the bowl with pure white paint. On the table in front of me, however, the real wall looked pale blue near the window and warmer beside the wooden cupboard. My teacher asked me to compare the wall with a piece of white paper held beside it.

The paper made the difference easier to see. I had been painting what I knew about the wall rather than the colour it appeared to be in that light. I mixed a small amount of blue into one area and a trace of yellow into another. The bowl began to seem part of the room instead of an object cut out and placed against a blank background.

In your own words, explain two things the comparison with white paper helped the narrator understand.