Katcher, Philip. The American Provincial Corps, 1775-1784 ç (Ospry Men-at-Arms Series). Osprey Publishing, 1973.
Very good, 40 pp. of illustrated text plus 8 pp. of color uniforms. Very good. Paperback. 
Initially British officials of the American Revolutionary War were reluctant to accept the offers of loyal subjects to form fighting units but eventually the potential of a Provincial corps was realized. Yet they never received the whole-hearted support of the British regular army and this was a factor in their eventual defeat. Nonetheless the Provincial Corps served with distinction even fighting against the Spanish in Nicaragua and the Bahamas and some remained in service for several more years by relocating to Canada. This book examines their experiences in this continental conflict and details their uniforms and equipment.