Are you looking to authentically replicate the real props, make an idealized version for display or is your focus on making it wearable?
For the exterior, let me suggest that you use decals and vinyl tape as much as possible. The original helmets had lots of that on them and much easier to apply than to paint. You can find the tape it in better stores that sell plastic models.
Ear cups can be yellow/tan or black. I don't know where the original ear cups came from, but they are oblong and big enough to fit your ears into.
The mics seen in ANH were not actually part of the helmet. A Racal RA-150 "Amplivox Minilite" head set was worn under the helmet. The head set is the same as the Rebel techs are wearing in the control room during the battle. In ESB and ROTJ, you could not see any mic tip -- only the boom that it could have been attached to.
In the past, people have bought ear cups and replica mic tips/head sets from Richies Armor. Ear cups for pilot helmets can be found on eBay, but authentic Racal head sets are more expensive.
I have heard that the authentic helmets were padded with pieces of yellow foam cut in a star-shaped ("petal", "maple leaf") pattern, in the same manner as Stormtrooper helmets were.
However, if you are wearing the helmet for some time (for trooping) then yellow foam can get soggy with sweat and can get smelly.
What I did for my costuming helmet was to cut ear cups and pads for the top and back of the head from foam and then coat them with some yellow/tan flexible faux leather I found. It looks a bit like the padding in the APH-6 helmet (which was cast to base the movie helmets on) and it also has the colour like yellow foam.
If you are interested in how other people have finished their costuming helmets (interior and exterior), then you could also check out
Rebel Legion's Pilot forum, especially the threads
X Wing helmet interior padding and
Show us your HELMET !!!!, but there are many posts to wade through.
If you are looking for an idealized interior, then there is a reference: Riddell's "Scaled Rebel Pilot Helmet". There is a picture
here