The Colors of a Room
Have the child look at one side of the room, then look away and tell all the colors he saw there in pictures, draperies, etc. Have him look at a certain picture for about five seconds and turn away and see how many of the colors in it he can recall.
Use a row of books on the shelf for another test. Have the child tell how many colors he saw in the row, and, if possible, how many books.