Which medication among the following is known to cause red tears as a side effect?

Rifampin is known to cause red tears among its side effects due to its ability to turn bodily fluids, including tears, a reddish color. This occurs because rifampin is a potent antibiotic that affects the liver's metabolism of various substances and can alter the color of secretions. Its mechanism involves the formation of metabolites that have a reddish hue, which is easily noticeable in tears, urine, and sweat.

The other medications listed do not typically cause similar changes to tear color. Isoniazid and Ethambutol primarily impact the lungs and are used in conjunction with other drugs in tuberculosis treatment, but they do not have this particular side effect. Vancomycin, while often associated with other side effects such as "red man syndrome" when infused rapidly, does not alter the color of tears. Thus, rifampin’s distinctive effect on tear color makes it the correct answer to this question.