Yellowish teeth are very common and often caused by surface stains or natural enamel changes. For daily care, look for whitening toothpastes containing mild abrasives like hydrated silica or low-concentration hydrogen peroxide to gently remove stains. For more effective and safer results, I recommend consulting a dentist. They can offer professional in-office whitening treatments using hydrogen peroxide or carbamide peroxide gels tailored to your teeth. Please avoid harsh home remedies like charcoal or lemon juice, which can permanently erode your protective enamel. Brushing twice daily, flossing, and limiting staining drinks like coffee or tea will also help maintain a brighter smile.