Since I'm considering buying the figure myself, your post was really helpful. The quality of the painting and shading is great as far as my limited personal skills can assess. A lot better than most of my efforts!!! I've been interested in WWI for the past 30 years, but only been painting figures for about 2 years.
Personally, I'm sort of compulsive and zealous about historical accuracy, but not everybody agrees with that approach. Some see that issue as much less important and want to concentrate on the enjoyment of the hobby itself, the craftsmanship of painting, etc. If you are in the latter camp, feel free to ignore all the rest of my comments.
In my opinion, I think you may have gotten the feldgrau uniform colors looking more like WW2 than WW1. To the best of my ability to determine feldgrau from WW1 period was usually a lighter color, more washed-out looking than in WW2. References attribute this to variations in dye lots and different contractors supplying cloth, etc., and it was about as true for German makers as for French, British, etc. The Austro-Hungarian and Italian uniforms changed dramatically to the point that each was using their enemies captured uniform cloth, etc. Confusing, huh? Although I haven't read this, I would also guess there were changes in dye and textile technology from, say...1917 to 1943, that would lead to greater color fastness of textiles.
Maybe some new, best quality WW1 feldgrau uniforms might be near the shades you used on the figure, but, according to the references I've used in the past, most of them would be lighter or in the case of Jaeger units, lighter and with a shade of green added. And after a period of field use, the colors would deteriorate a lot.
Yes, I know...some of the box art clearly shows darker feldgrau uniforms, etc. I can't account for that. Most of the paint vendor pre-mixed feldgrau and "German uniform" colors really seem to be intended for WW2 uniforms, not WWI.
In summary, take a look at the German uniforms on the JonSmith Modellbau web site. And again, feel free to disagree...
All the best!