you have a few options...all depends on how much you want to spend.
Their are two companies that offer smoked film that is durable..rockblocker and laminex. The advantage to this is that since it is only a film, it can be removed without much effort. This is good if you get a ticket or just decide you don't like it after all.
Your other option is having them painted. The two best ways have been mentioned. Either buy a can of nightshades (made by vht) or create a mixture of black paint and clear coat. If you are not familiar with painting and want it to come out real smooth and shiny looking you are best off getting it done at a bodyshop. If you do it yourself, do light coats and let them dry before putting on the next coat. Once you get the desired darkness, you should wetsand them and then do a few coats of clear and then wetsand again. Finish up by polishing them.