**Core Concept**
The cariogram is a graphical representation of an individual's risk for developing dental caries (tooth decay). It incorporates various factors, including diet, oral hygiene, and saliva flow, to assess the likelihood of caries occurrence.

**Why the Correct Answer is Right**
The cariogram uses different colors to indicate the level of caries risk, with green representing a low risk. This is because individuals with low caries risk tend to have a healthy diet, good oral hygiene habits, and adequate saliva flow, which helps to neutralize acid and remineralize teeth. The green color indicates that the individual is at a lower risk for developing dental caries.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because red typically represents a high caries risk, not a low one.
**Option B:** Incorrect because blue is often associated with moderate caries risk, not low risk.
**Option C:** Incorrect because yellow may represent a moderate to high caries risk, but not specifically low risk.

**Clinical Pearl / High-Yield Fact**
A cariogram can help identify individuals at high risk for dental caries, allowing for targeted interventions to prevent or mitigate the disease.

**Correct Answer: C. Yellow**