How do I keep my black trousers black?

1. Avoid excessive washings.

2. If black trousers are primarily wore indoors- you can get away with wearing them four or five times between washings.

3. When the washing machine is ready to load, turn the trousers inside out to minimize color loss caused by the friction from rubbing against other clothes, then choose a small, delicate cycle. The colder the temperature, the better, since warm water tends to break down fibers and fade clothes faster. 

4. Then hang or lay the pants flat to dry, don’t throw them in the dryer(as the lint in the dryer drum gets accumulated on to these black trousers)

5. Steam Iron the black trousers for better look and feel.