Differences between Shure E4 and E4c?
 

Title says it. Both the E4 and E4c models have the same sensitivity and impedence, so...
1. is there any difference between the two in terms of sound quality or noise isolation? I have seen the E4 in grey (my first choice in color) and the E4c in white and black.
2. what does the "c" mean?

I think c stands for commercial. They are the same earphones, but come with a different set of accessories.

The "c" stands for "consumer" version. The E4 is intended for the professional market, so you will probably need to go to a professional audio dealer to purchase it, and probably you will need to order some of the accessories you get included with the consumer version separately, particularly the custom ear molds that the E4's fit into through your audiologist. Otherwise, exactly the same components are used in the E4 and E4c, so there should be no audible difference between the two.

Yes, you are correct. I finally found an authorized Shure dealer website that specifically says c is for consumer. This dealer however will match other lower prices and include the items typically sold with the consumer version (ie attentuator, case, the different types of molds, etc). Thanks for your help.