hi the change in colour of your teeth has many reasons like not getting cleaning done regularly, intake of coloured beverages and more I advice you to visit a dentist nearby get a scaling done. You can also use some toothpastes which reduce your sensitivity. If you are very concerned on part of colour of the tooth you can go with teeth whitening or veneers. Dr.Mandakini Mandakini dental clinic

Get ur teeth cleaned n then do proper massaging of ur gums... Brush twice with soft tooth brush .. Use sensitive tooth paste along with the normal paste if u ve too much of sensitivity ...