**Core Concept**
Metamorphic calcification is a type of calcification process where a previously formed organic structure undergoes calcification, resulting in a change in its appearance, particularly in its color. This process is often seen in the context of atherosclerosis and is characterized by the deposition of calcium salts in areas of necrotic or damaged tissue.

**Why the Correct Answer is Right**
The color change in metamorphic calcification is primarily due to the deposition of calcium salts, which alter the optical properties of the affected tissue. This process is often accompanied by the formation of a fibrotic capsule around the calcified area, which further contributes to the color change. The calcification process involves the activation of various enzymes, including alkaline phosphatase, which plays a crucial role in the deposition of calcium salts.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the color change associated with metamorphic calcification.
**Option B:** This option is incorrect because it does not account for the underlying biochemical processes involved in metamorphic calcification.
**Option C:** This option is incorrect because it does not accurately describe the changes that occur in the tissue as a result of metamorphic calcification.

**Clinical Pearl / High-Yield Fact**
The color change in metamorphic calcification is often accompanied by a change in the texture of the affected tissue, which can be described as hard and gritty. This texture change is due to the deposition of calcium salts and the formation of a fibrotic capsule around the calcified area.

**Correct Answer: D.**