Subject: What are the colors of the rainbow? Why can't you see some if them?

What are the colors of the rainbow? Why can't you see some if them?
I know there are more colors to a rainbow that meets the eye because
in school we have talked about them.  But two things don't make 
sense, why can't you see some them and how did scientists find out  
about them if you can't see them?  I would appreciate if you write 
back and answer my question, Thank You.

                                     Sincerely,
                                      Jade

Re:What are the colors of the rainbow? Why can't you see some if them?