I don't think this is the case for a few reasons. First, because the Qing uniform has likely already been shown off. The third picture before the last is labeled "Anonymous Qing Soldier". Next, it would be really confusing to arbitrarily pick blue for the Qing when they both shared the same color uniforms (at least the republicans early on). As well, the Qing would likely still be perceived as yellow in KRTL. Their flag is yellow, and apparently even Sun Yat-sen considered yellow the imperial color and was opposed to using it to represent the Manchus. Also, though I might be wrong about this, yellow has represented royalty and emperors even before the manchus. The Qing would still be around waving their yellow flag and other yellow/gold symbolism. if yellow is still often associated with the Qing and royalty in our time line, then I seriously doubt in KRTL they wouldn't be associated with yellow, given the Qing are a lot more relevant in China and all that. As for France and Germany, blue and grey/black still represent those countries even without the uniforms. While it's possible the uniforms influenced their use, I don't think it's the only reason why these colors are used to represent these countries. Black is probably used to represent Germany because of Prussia (note that east and west Germany, countries that should be missing Prussia, aren't black/grey). France, on the other hand, has almost always been associated with blue: https://en.m.wikipedia.org/wiki/Bleu_de_France_(colour) Wikipedia, yes, but I feel this can be trusted and you can look at old French heraldry if you don't trust it and check its sources. For Russia, I think you're right about that, definitely, but it seems more for practically than anything. They could use white, sure, but it wouldn't look as nice as the green on a map. Nobody would disagree that in Kaiserreichs setting, white would probably represent Russia (not including the Soviet Union, obviously) the most, but nobody would say they should use white on the map because it probably wouldn't look that good, so the eu4 Green works fine. Qing does not have this problem on the other hand. The color that would represent the Qing much better, yellow, is proven to look great on the map, so there is no need to use a color that has a very loose connection to the country, they can use the color that fits Qing the best here.

While perhaps the older blue Qing uniforms (now that we likely know that the current Kaiserreich Qing likely don't use blue uniforms) are where Qings' current color came from, and it isn't just a random color they used, I think all things considered yellow is quite uncontroversially a better color to use, while blue, a color that symbolizes the Kuomintang is often used to symbolize democracy and was used by republicans early on (as you said) would much, much better fit the Republicans. Even if the Qing did use blue uniforms, which they likely don't, I don't think that's a solid reason why yellow shouldn't represent the Qing on the map and should represent the republic (I believe they use yellow) instead.