Paper plays a vital role in color reproduction because its optical and surface properties impact how light is reflected and therefore how color and tonal values appear when printed. The more light the paper is capable of reflecting, the wider the range of contrast and color that is possible on the final printed piece.

Optical Properties of Paper
The critical optical properties of paper that impact color and contrast are its brightness and whiteness values.

The brighter and whiter the paper the more it reflects light, enabling the printed piece to achieve higher contrast as well as a wider gamut of color. Gloss coatings on paper also enable it to reflect more light, which is attributed to making colors pop. This is especially helpful in making photos appear more colorful and saturated.

The less bright and white a paper is, the lower its ability to reflect light, and therefore the narrower the amount of contrast and color that is possible in the printed product. This, in fact, can be a desirable quality, as documents with more text and less photos would be better served by a paper that is more subdued, allowing the readers eyes to focus on blocks of type without being distracted by paper glare.

Surface Properties of Paper
Surface properties refer to the texture and finish of the paper. Smoother coated paper is more reflective because light is not as diffused as it would be by the texture of a coarser uncoated paper. Think of how much more reflective a fresh piece of aluminum foil is versus a used one with many creases and wrinkles.