The Perry website has an article by Brendan Morrissey which will answer all your questions. However, and in a nutshell :
* The "leather" caps were actually old felt cocked hats cut to look like something resembling a light infantry cap. They appear to have been worn by all of Burgoyne's British regiments, including those that stayed in Canada and did not participate in the Saratoga campaign. Only officers seem to have clung to their hats.
* Grenadiers probably wore the same cut-down hats as the rest of the rank and file rather than their expensive bearskins, although there is no definite evidence one way or the other (grenadiers were issued a felt hat every year for fatigue duties, whereas the precious bearskins were expected to last at least a decade).
* Regimental facings : see the Perry website, they're all listed there.
* Brunswick musketeers wore cocked hats. Only grenadiers had the Prussian style mitre cap.
* Continental uniforms : largely unknown. 1777 was a chaotic year for the Americans as far as supplying the army was concerned. Many regulars may have worn hunting shirts or civilian clothes, although some regiments are known to have received military coats. Unfortunately, coat colours and facings remain largely unrecorded. For what it's worth, brown and blue coats are most likely for New Hampshire and Massachusetts units.
Use the link below to go to the Perry site and use the drop-down menu to select AWI articles :
http://www.perry-miniatures.com/index2.html