I have seen color illustrations and accounts that said the standard color for a 1944 German uniform was something called 'slate gray'. Was this a radically different color from earlier uniforms or just a gradual shade difference? And if it was a very different color from earlier field gray, what was the reason?

IT was just the ever expanding evolution of German uniforms. The color is really a green color. Pollyscale has it and there are otheers fer sure.

Chris

Feldgrau was a gray green dye developed for the woolen uniforms worn by foot soldiers in temperate climates. Later in the war, standards were relaxed, and a shoddy rayon/wool blend was substituted. These batches of cloth were often a neutral gray, or at least less green (the color standard didn't officially change). In some cases, uniforms were manufactured from confiscated Italian or Czech military fabric, so that also affected the final color. Given the number of factories and subcontractors involved, there was tremendous variation in color, especially after you include the fading seen on uniforms after issue.