Peter - My guess is that the term "blazons" refers to a type of flag, such as camp colours (independent companies had no large "regimental" colours) or possibly pipe banners. Until the 1751 Royal Clothing Warrant forbad the practice, commanding officers were permitted to have their coat-of-arms (i.e., armorial blazon) depicted on their unit's colours and drums, and their field musicians (such as pipers and drummers) may have worn a uniform in the livery colours of their commander, rather than the usual "reversed" coloured uniform coats.

"Blazons" is an obscure term that I've not seen with regard to 18th c. British uniforms. When I get home (I'm at work), I'll check my copy of Thomas Simes' "Universal Military Dictionary" of 1768 to see if the term is listed there. If it is not, one must keep in mind that the term may have been used (at least in Scotland) in the 1720's but passed out of use by the 1760's.