The main causes for orange tongue are usually acid indigestion or heartburn, or an imbalance of the microorganisms that live in your mouth, especially on your tongue. The latter will usually happen after a round of antibiotics. As always, you should be seen by your doctor for a proper evaluation in case it is an uncommon cause.
Regardless of the cause, you should gently brush your tongue in a downward motion away towards the front of your mouth (leading away from your throat) several times throughout the day, followed by a rinsing of cool (not cold) water mouthwash such as Listerine Antiseptic Mouthwash, ACT Total Care Rinse or Scope Mouthwash Outlast Long Lasting Mint. This will relieve the physical symptoms and will help restore balance.