Generally colour of your teeth is dependent on the thickness of enamel and colour of dentin which are layers of the tooth. It remains constant like skin or eye colour but sometimes deposits on teeth  or loss of enamel ( outer layer) may give it yellowish appearance. A scaling or cleaning would be beneficial to remove the surface deposits but the natural colour of the tooth will not change. For that bleaching procedure can be done... Bleaching is done only in patients with healthy enamel or else it can cause sensitive teeth. Best to visit a dentist for a check up to consider your options.