**Core Concept:** Putrefaction is the process of decomposition of organic matter, particularly organic tissues, due to the activity of microorganisms like bacteria and fungi. The initial color changes observed during putrefaction are associated with the activity of certain enzymes produced by these microorganisms.

**Why the Correct Answer is Right:** In the early stage of putrefaction, the primary color change is due to the activity of enzyme called protease produced by bacteria, particularly Clostridium perfringens. This enzyme breaks down proteins into simpler compounds, resulting in a brownish-black color known as lividity.

**Why Each Wrong Option is Incorrect:** Option A (yellow) is incorrect because the yellow color seen in some cases is due to the presence of heme pigments (such as hemoglobin) that are not affected during the early stage of putrefaction. Option B (red) is wrong because putrefaction starts with a brownish-black color due to proteolysis, not redness. Option C (green) is incorrect because the green color is typically observed later in the process, when putrefactive gases like methanethiol are produced. Option D (white) is wrong because the presence of microorganisms and enzymes involved in early putrefaction prevents the formation of a white color.

**Clinical Pearl:** The correct answer, brownish-black color (lividity), is an important clue in forensic pathology to indicate the time of death, as it is influenced by the gravitational force and the rate of putrefactive enzyme activity.

**Correct Answer:** C. brownish-black (lividity)