There is indeed B and A-Wing pilots with X-Wing style helmets on... Not to say they aren't X-Wingers, or some other pilot, but I've always argued those guys in the past. They're noticeable as Han/Lando say their goodbyes on Home One's hangar floor.
Ultimately I think the whole "color = pilot duties" is stupid... Same with the helmets. The helmets are probably handed out to various squads, and you get what's available. One may be a Rebel manufactured, or several may come from sympathetic manufacturers, and some may just be stolen/found/donated. Considering Han has a helmet in his ship that is identical in every way to the ANH pilot helmets, I'm guessing it's just a popular helmet.
In the briefing scene, A-Wingers are seen with the "Tycho" style helmet and the cloth liners on... Yet we see A-Wingers with a totally unique helmet (The upcoming Arvel Crynyd has this helmet on) in the movie's combat scenes.
And you're right, that is a dude jedipurge... Weird. I had no idea who that person was actually but thanks. So one female pilot... Good to know.
If it's of any interest to anyone, the original X-Wing game actually had a "randomized" thing that put a picture, supposedly of your character, up on the screen. You'd change the name and you'd get a different look. it included everything from Mon Calamari pilots cobbled together from film pilot images and the Mon Cal officer images, to all kinds of pilots and uniform colors with helmet combos to match. Basically, any pilot could have on any gear at any time, and it didn't really matter.
The white suited pilots never made it tot he film for one reason or another, but the only white suited pilot ever pictured (as far as I know) is Ten Numb. And ultimately he makes it to the film, but in red, during the Ewok celebration. I've heard people refer to him as Nein Numb also, but I think there's a shot of Nein at the party in his Falcon get-up, and Ten is seen in full B-Winger gear, but all in red.
Somewhere I read the B-Winger's suit was dyed red at a later time just on a Lucas whim too... Forget where but I know it was a making-of type book.