Here are illustrations of the various MERDC (Mobility Equipment Research and Development Center) camouflage colors on the M109 template. The colors will vary depending on your computer monitor settings, but they illustrate the basics of the schemes and variations. The title of the scheme is followed by the color names, the color Federal Standard numbers, and the illustration.
The Winter Verdant scheme was typically used on vehicles based in Europe and was likely the most common MERDC scheme. The Summer Verdant scheme was most commonly used on vehicles based in the United States. The Gray Desert scheme was used on vehicles based at Fort Hood in Texas and some units based in California. The Red Desert colors were used by New Zealand army units.
The official patterns were not always followed by some units, but then there are examples where the patterns were carefully followed. Some US Army units in Europe would omit the Sand color in the Winter Verdant scheme which can easily be confused with the later NATO type three color camouflage.
Winter US & Europe-Verdant
Forest Green, Field Drab, Sand, and Black
(34079, 30118, 30277, 37038)
Snow Temperate with Trees and Shrubs
Forest Green, White, Sand, and Black
(34079, 37875, 30277, 37038)
Snow-Temperate with Open Terrain
White, Field Drab, Sand, and Black
(37875, 30118, 30277, 37038)
Summer US & Europe-Verdant
Forest Green, Light Green, Sand, and Black
(34079, 34151, 30277, 37038)
Forest Green, Dark Green, Light Green, and Black
(34079, 34102, 34151, 37038)
Sand, Field Drab, Earth Yellow, and Black
(30277, 30118, 30257, 37038)
Earth Red, Earth Yellow, Sand, and Black
(30117, 30257, 30277, 37038)
It is overall temporary white and is simple enough that it does not require illustration.