Martyn...I don't know...the fact was that...Scott's Army could not procure enough blue fabric to clothe his men...
take the rest of the myth with a grain of salt...but it is an interesting read...
http://en.wikipedia.org/wiki/Battle_of_Chippawa
Scott had been unable to obtain enough regulation blue uniforms for his men. Although they had been manufactured and sent to the northern theater, they had been diverted to Plattsburgh and Sackets Harbor. Sufficient uniforms were scraped together to clothe the 21st US Infantry. The United States Army's Commissary General, Callender Irvine, hastily ordered 2,000 uniforms to be made and dispatched to Buffalo for Scott's other units, but because there was insufficient blue cloth, short jackets of grey cloth were used instead.
As the American line continued to hold steady under British artillery fire, British General Riall realized his error and supposedly exclaimed his famous phrase "Those are regulars, by God!"...mistaking the gray jackets as militia...(Scott appears to be the only source for Riall's utterance; there is no record of it in any British source.)
The Corps of Cadets of the United States Military Academy at West Point wear grey parade uniforms, but the assertion that they were adopted in commemoration of Scott’s troops at Chippawa appears to be a legend. The reasons given in 1816 for its selection were simply that it wore well and was considerably cheaper than the blue one.