Having irregular periods .bleeding time to time for two weeks but not fully and colour of blood is different.is that sign of cancer?

Not at 18 years old: Irregular periods are one of the most common problems obgyns treat. If this is one time problem it usually resolves on its own. If this is a recurring problem you should be evaluated. Infections & hormonal changes can cause spotting. If there is a concern for pregnancy then do a home pregnancy test . There are many options available to help regulate the menstrual cycle. Schedule a visit.

Not necessarily: Not necessarily a sign of cancer, especially at your age. you need to be evaluated by a GYN. At your age, it's usually just a hormone imbalance.