Subject: Colors; wavelengths not adding up for me

If red has the longest wavelength and purple has the shortest 
wavelength, how is it that red and blue (blue being presumably a 
medium wavelength) make purple? Why doesn't the longest plus the 
shortest equal the medium?

How is it explained that the colors we call primary (red, blue, yellow 
- because no colors can be mixed to create them) and the colors we 
call secondary (green, purple, orange - because we mix the primary 
colors together to make them) are interspersed perfectly in the 
rainbow? (except for the ending - purple which should flow back in a 
circle to the beginning!) It seems to me that one color flows into the 
next, since its rate of motion is what determines its color.

Are there colors that cannot be seen by the human eye that when mixed 
together make up our so-called primary colors?

Have the vibrational frequencies of the colors been translated to the
scale of sounds as in the musical notes? For example does the 
vibrational frequency of one color equal a particular note? If this is 
possible, can we create a visual symphony that can be seen by the 
deaf? 

If I am on the right track with this line of thinking then does it 
follow that the frequencies of sound that are out of our range of our 
hearing are in line with the frequencies of light that out of our 
range of seeing?

Thanks for your time.

Re: Colors; wavelengths not adding up for me