I use green, and generally prefer Novak's or Trijicons. Installing night sights is pretty easy and most dealers can handle the job. I don't think there is a best although there are personal preferences. They all use tritium inserts, and you can have inserts installed in existing sights although that is pricey. Otherwise, you will probably pay around $100 to 150.

I have no idea what shops are available that are close to you, but you should at least be able to find somewhere in Portland.