In general, your vision must be CORRECTABLE (with glasses, contacts, or surgery or a combination of these) to 20/40 for a Private Pilot Certificate and to 20/20 for a Commercial or Flight Instructor's Certificate (with no other major vision problems or diseases).  Surgery or Lasik surgery is acceptable, as long as the surgery is successful and there are no complications that negatively affect your vision and you can pass the normal FAA Medical Exam.  Partial color-blindness is not a major impediment.  Pilots can be granted a medical waiver if they can distinguish the colors (red, green and white) of an FAA tower "light gun" used to signal pilot without radio communications working.  The colors of the light gun signals are also specially formulated so that even most color blind people can see them.