I see the confusion. Look at page 5.

Under HLA-B*1502,

"suggests higher risk of serious dermatologic interactions including toxic epidermal necrolysis (TEN) and Stevens-Johnson syndrome (SJS) when taking certain mood stabilizers"

So for that patient, red means the patient has an increased likelihood for a negative interaction with mood stabilizers.

And on page 6,

CYP2C19
"This genotype is most consistent with the ultrarapid metabolizer phenotype. The patient may have increased enzyme activity as compared to individuals with the normal phenotype." On the flip side, CYP2D6 suggests that your enzymes don't metabolize certain things well.

" In particular, CYP2D6 is responsible for the metabolism and elimination of approximately 25% of clinically used drugs" - Wikipedia

CYPD2C19: "The gene encodes a member of the cytochrome P450 superfamily of enzymes. These proteins are monooxygenases that catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids and other lipids. This protein localizes to the endoplasmic reticulum and is known to metabolize many drugs. - Wikipedia

So it's just saying possible side effects. Like, you are at risk for increased cholesterol or increased body fat with the existence of the CYPD2C19 gene. But with CYP2D6, you metabolize the med well and may need a lower dose.