Final answer:
The red color of the Serratia marcescens colonies is an example of pigment production.
Step-by-step explanation:
The red color of the Serratia marcescens colonies is an example of pigment production. Many bacteria produce intracellular pigments that cause their colonies to appear different colors, such as yellow, pink, purple, or red. Some bacteria do not produce any pigment and appear white or gray. In the case of Serratia marcescens, the red pigment is produced at room temperature, giving its colonies a red color.