reading two:

The flat surface that a human works on/at is called the picture plane. Three demensional space has height, width and much depth to it for it to be legit. Flowing space isnt always clear nor the best choice in many artists/photographers eyes. You can add tints by adding white within the picture because it will dull it up a little bit depending id you know what your doing or not. Colors such as white, gray, and black are classified as neutrals. Obviously color comes from the right lighting corresponding to the picture.