A problem with the form of converting ply to fbx - assimp

Question

We are currently in the process of converting PLY or PCD data to FBX.
I did the conversion using the Assimp library as shown below, but I found a problem with missing colors.
May I know where is wrong?
#include <assimp/Importer.hpp>
#include <assimp/scene.h>
#include <assimp/postprocess.h>
#include <assimp/Exporter.hpp>
#include <System.h>
int main(int argc, char* argv[]) {
Assimp::Importer importer;
const aiScene* scene = importer.ReadFile("/app/test.ply",
aiProcess_Triangulate |
aiProcess_JoinIdenticalVertices |
aiProcess_SortByPType);
// Check that the import was successful
if (!scene) {
std::cerr << "Failed to import file: " << importer.GetErrorString() << std::endl;
return 1;
}
// Iterate over all the meshes in the scene
for (unsigned int i = 0; i < scene->mNumMeshes; ++i) {
aiMesh* mesh = scene->mMeshes[i];
// Check if the mesh has color data
if (mesh->HasVertexColors(0)) {
// Set the number of color components to 3 (for RGB)
//mesh->mNumColorComponents = 3;
// Allocate memory for the color data
mesh->mColors[0] = new aiColor4D[mesh->mNumVertices];
// Fill in the color data (for example, set all vertices to red)
for (unsigned int j = 0; j < mesh->mNumVertices; ++j) {
mesh->mColors[0][j].r = 1.0f;
mesh->mColors[0][j].g = 0.0f;
mesh->mColors[0][j].b = 0.0f;
mesh->mColors[0][j].a = 1.0f;
}
}
}
// Export the scene to fbx format
Assimp::Exporter exporter;
exporter.Export(scene, "fbx", "output.fbx");
return 0;
}