Hmm, yeah, I couldn’t find it either, though it seems kinda strange to me, that FColor isn’t exposed to BP.
However, it should work if you create a C++ Blueprint Callable Function that takes in a TArray of FLinearColor and returns a TArray of FColor and simply converts one to the other. FLinearColor even seems to have a “ToFColor” function. That way you could create your color array procedurally in BP, convert it and then pass it into CreateMeshSection; although that would add the overhead of converting each FLinearColor. If you get performance problems you might then think about creating the colors completely in C++.