when having a laser, what different colours can they go and what makes them go different colours, also how can lasers

Question: when having a laser, what different colours can they go and what makes them go different colours, also how can lasers change the future?:)
- Keywords:
  colour,
  future
Asked by ilovenerdss to Tom on 26 Jun 2012.
- Tom Lister answered on 26 Jun 2012:
  
  It depends what material you make the laser out of, but you can have any colour you like. How are they going to change the future? Perhaps they will be used for mining deeper?

Question: when having a laser, what different colours can they go and what makes them go different colours, also how can lasers change the future?:)