Earlier quoted context omitted.
The whole point of the pamphlet is they shouldn't have to in order to be accepted by the American troops, but a white French person with sufficient linguistic and cultural flexibility could pass for a white American, and largely would in contexts where they did not have to speak. And black person could never do the same.
A black person could pass for a white person in contexts where did not have to show their skin colour, it's not that different or even rare.
So basically on the phone or email only.
In every other scenario, like when walking down the street or encountering law enforcement, it's pretty much impossible.