i am getting no pain from it evern hot or cold can i use crest white strips on it

it sounds like the nerve inside the tooth may have died. the sure way to test this is by holding an ice cube against it. if you can't feel the ice cube on the tooth then sure enough the tooth may no longer be vital. if you can feel the coldness from the ice-cube your tooth is still alive but i'd get it checked by a dentist to make sure it's ok.

this means getting to your dentist soon, as the tooth may continue to darken. your dentist can lighten the tooth for you if it's caught soon enough with a bleaching system. the tooth can also be veneered. colgate strips, i doubt they would work as they remove extrinsic stains (tea, coffee etc). decay products darkening a dead tooth are intrinsic stains and need more work.