**Core Concept**
The Fouchet's test is a biochemical test used to detect the presence of bilirubin in a sample. It is a qualitative test that relies on the oxidation of bilirubin to form a green pigment, which is indicative of a positive result.

**Why the Correct Answer is Right**
The Fouchet's test works by oxidizing bilirubin using ferric chloride, resulting in the formation of a green pigment. This reaction occurs because bilirubin has a specific molecular structure that allows it to be oxidized by ferric ions, leading to the formation of a green-colored compound. The green color is a characteristic feature of a positive Fouchet's test result.

**Why Each Wrong Option is Incorrect**
**Option A:** Red is not the correct color associated with a positive Fouchet's test result. While some biochemical tests may produce a red color, the Fouchet's test is specifically associated with a green color.
**Option C:** Violet is not the correct color associated with a positive Fouchet's test result. The Fouchet's test does not involve the formation of a violet pigment.
**Option D:** Yellow is not the correct color associated with a positive Fouchet's test result. While bilirubin itself has a yellow color, the Fouchet's test involves the oxidation of bilirubin to form a green pigment.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the Fouchet's test is a qualitative test, meaning it can only provide a yes or no answer to the presence of bilirubin. Quantitative tests, such as the van den Bergh test, may be used to measure the concentration of bilirubin in a sample.

**✓ Correct Answer: B. Green**