When you asked this four years ago, this was my response:

I've previously written an answer to a similar question, which is reproduced below:

For some African-American soldiers who participated in the First World War and the subsequent historiography on the topic, the French have a special place. According to this narrative, the French were kind, curious, and far more welcoming than white Americans. In fact, one could go as far as to say that the French population treated African-Americans as equals. In an alternative narrative, African-Americans met with an equal amount of racial prejudice from the French population who avoided them, called them names and held a hostile attitude towards them.

Which narrative is true? Undoubtedly, both of them are which reveals the complexity of the subject. The question therefore is why? Why did both extremes exist at the same time?

Scholars have given many explanations as to the first, positive narrative. Historian Chad L. Williams in his book Torchbearers of Democracy: African American Soldiers in the World War I Era writes that "the glowing accounts of the French stemmed not so much from perceptions that the French lacked racist sentiments but from the fact that white soldiers and officers regularly acted with such hatred." As you point out in your question, the French population showed a strong racial prejudice towards colonial troops from French African colonies. This includes a racial perception of, for example, West African soldiers as childlike or savages taking their first step into the "civilized" world. The French government made many attempts to try and make West African soldiers "acceptable" for the French population by portraying them in a specific racialized way. This image of the French African soldier was contrasted with that of the African American soldier. Suddenly, here was a black man from the west, a civilized black man in contrast to the savage Africans, whose long presence on the American continent had civilized them and evolved them (noire évouée). This was proof, in French eyes, of the civilizing influence of the west and a justification for their own civilizing mission in Africa. Encountering an African American soldiers was therefore a "safe" alternative to the more savage and childlike French African. These more cordial encounters were not without racism, but as Williams points out above, it paled in comparison to the outright hostility from white Americans.

This, in its essence, is the core of the complex subject. Racism was a present factor in any encounter with French civilian and soldiers, but it expressed itself in different ways than that of white Americans. Without a doubt, the most vile racism that white Americans spouted at African Americans were also shared by some French, in particularly in portraying black men as rapists and "defilers of white women". This ties in to racial tensions between French men and men of African descent over white women. Furthermore, there were also labour tensions as white French dockworkers saw their jobs being taken over by black dockworkers for the war effort. How much influence American racist stereotypes had on the French population is hard to say, in particularly in light of how African Americans were seen in comparison to white Americans (the latter being more trouble than the former). Additionally, one final point has to be made: French civilians and soldiers knew that African Americans were only there temporary. They were only passing through and once the war was done and over, they'd go right back home. This meant that a different attitude towards them could be justified. Colonial soldiers were not extended the same treatment.