Can give you a good suggestion by taking a look at it. If you can post a picture that would be great.
Discolouration can probably be due to accumulation of calculus around the teeth which are yellowish deposits on the surfaces of teeth that are formed due to inadequate cleaning of the teeth or it could be stains that are either intrinsic or extrinsic.
Next Steps
if the cause of the discolouration is calculus or extrinsic stains then a regular dental cleaning is advised.
Health Tips
could help you further if you could get in touch in the chat section.