Final answer:
Bacteria exhibit a variety of colors depending on their intrinsic pigments, like bacteriochlorophylls and carotenoids, and the environment they inhabit. The purple color in purple sulfur bacteria and the varying hues in phototrophic bacteria are examples. Bacteria can appear differently when stained in laboratory procedures, such as Gram staining, which can also indicate their identity.
Step-by-step explanation:
If bacteria are alive and capable of producing pigments, the biological indicator such as the culture media may change color. Many bacteria produce intracellular pigments that lend a distinct color to their colonies. For instance, bacteria like the purple sulfur bacteria contain pigments called bacteriochlorophylls and carotenoids, giving them a purple hue. They live in water as strict anaerobes and perform a form of photosynthesis.
The color a bacterium turns can be affected by many factors, including the type of medium they are growing on and its metabolic processes. For example, Halobacteria growing in salt ponds give them a distinct purple color, and certain types of phototrophic bacteria perform photosynthesis and present colors that range from orange to red to purple to green depending on the pigments such as carotenoids they contain.
When using Gram staining procedures, bacterial coloration after staining is also a method of identification. As an example, L-form bacteria that lack a cell wall wouldn't retain the crystal violet stain in the Gram staining process and might not be colored by this approach. Many types of bacteria can be seen in a single microscopic field based on the variety of shapes, arrangements, and colors.