My son is is potty training. when he urinates its yellow. he has no other sc of illness but sometimes urine drops on seat dry brownish red. worry?

Urine: Have his urine checked to rule out hematuria (blood in urine)

Certainly see his: pediatrician for a urinalysis to rule out blood, bacteria, etc., as Dr. N. advised. Some foods and medications can turn urine red or brown, like beets, blackberries, rhubarb (red) or fava beans, aloe (brown). Laxatives with senna or cascara can turn urine brown. But rule out medical causes first.