Are there colored eye implants available that will correct astigmatism and nearsightedness? I'm thinking about eye implants so that I won't have to wear contacts any longer. I'd also like to change my dull brown eye color to green. Is such a procedure pos

No. While there are various types of lens implants to correct your vision, none of them will change your eye color. Stick with your colored contacts.
Colored . Colored implants are offered for injuries for the eye on limited basis through fda humanitarian exemption, but they don't correct vision. They are experimental and trials have been yet to be started in the United States for elective cosmetic reasons. You would need to have lasik to correct vision and the implants later to change the color of the eye. There is a company working on laser that would turn brown eyes closer to blue eyes by removing the brown pigment. This procedure is probably 3-4 years away to the start of clinical trials.