Which factor does NOT affect the shape of a protein?

The shape of a protein is primarily determined by its amino acid sequence and the interactions that occur among the amino acids and with the environment. Factors such as salt concentration, pH levels, and temperature can significantly impact protein folding and stability.

Salt can influence ionic bonds and electrostatic interactions between charged side chains of amino acids, potentially leading to changes in the protein's conformation. pH affects ionization states of the amino acids, altering hydrogen bonding and ionic interactions that are crucial for maintaining a protein's three-dimensional structure. Similarly, temperature affects the kinetic energy of molecules and can lead to denaturation, where proteins lose their functional shape due to the breaking of non-covalent interactions.

In contrast, color does not have any bearing on the structure or folding of a protein. It is not a factor that influences the interactions between amino acids or the protein’s environment in any way related to its shape. Therefore, it is accurate to conclude that color does not affect the shape of a protein.