**Core Concept**
The discoloration of bruises, also known as ecchymosis, is a result of the body's attempt to repair damaged blood vessels. The initial blue coloration of bruises is caused by the presence of deoxyhemoglobin, a breakdown product of hemoglobin.

**Why the Correct Answer is Right**
Deoxyhemoglobin is formed when oxyhemoglobin is reduced to its deoxygenated state, which occurs when red blood cells are damaged and release their hemoglobin content. This deoxyhemoglobin has a blue color due to the way it absorbs and reflects light. The blue coloration of bruises is typically seen in the early stages of healing, as the body is trying to repair the damaged blood vessels.

**Why Each Wrong Option is Incorrect**
* **Option A:** Not applicable, as the question does not provide a distractor for this option.
* **Option B:** This option is incorrect because the blue color of bruises is not due to the presence of bilirubin, which is a breakdown product of hemoglobin but is not responsible for the blue coloration.
* **Option C:** This option is incorrect because the blue color of bruises is not due to the presence of methemoglobin, which is a different oxidation state of hemoglobin that has a distinct brown or chocolate color.
* **Option D:** This option is incorrect because the blue color of bruises is not due to the presence of carotenoids, which are pigments responsible for the yellow or orange coloration of certain tissues.

**Clinical Pearl / High-Yield Fact**
It's worth noting that the color of bruises can change over time, progressing from blue to green to yellow as the body breaks down the hemoglobin and other pigments. This is why bruises often appear yellow or greenish-yellow in the later stages of healing.

**Correct Answer: B. Bilirubin is not responsible for the blue color of bruises.**