Perhaps bacon fat grey would be better, with egg yolk facings? Its better than fouling your regimentals I suppose!
The Standing Orders of the 13th, 1808, do have some instructions on saving the white shirts from excessive wear,
"In Gibralter, and other situations where the Men are expected much to be employed on fatigue parties, they will be permitted to have a check shirt or two, to save their white ones: they must, however be as frequently washed as the white.
Whenever a soldier shall be detected as having in his possession what is known as a false frill, or half-shirt, an article meant for the filthy purpose of hiding dirt, it is immediately to be burnt, and the man confined for disobediance of these orders."
On the Imperial service