First go for Scaling and polishing.  Next if intrinsic stains are still visible,  you can go for a professional teeth Whitening

Hello sir...   Discolouration of tooth is due to so many cause...    **plaque and calculus deposits(soft and hard deposits)    **intrinsic discolouration    ** smoking, pan stains, coffee and tea stains   **Flurosis... Clinical examination is necessary to rule out the cause.. For stains and deposits you need to go for scaling and polishing... It starts from Rs. 800 For instrinsic discolouration and mild flurosis..you need to go for bleaching it cost around Rs. 5000.....

If the yellowish discoloration is due to external stains- a scaling will help - 500-2000 INR If discoloration is due to intrinsic stains- bleaching is the option - 3000-8000 INR The normal tooth colour is pale yellow and not white Visit a nearby dentist to find out which procedure is necessary