When I use code vertexColors: true. I found that the other faces that were not in the coloring range were also colored
I solved it by building a new geometry from the faceIndexs of the model, will there be a better way to solve this problem？
It sounds what you did is just right. When you want to ensure vertex color definitions do not affect the final color of a specific face, you have to make sure no respective vertex hold a vertex color other than 0xffffff.