Vertex Color nodes connect to the corresponding connector of the Mesh builder node. Each next node is connected to the bottom connector of the previous Vertex Color node. These nodes are calculated in the same sequence.
These nodes also has additional Display options on the sidebar:
Allows the user to see the vertex colors in the viewport. It is like a Display panel > Display Properties rollout > Vertex Colors.
When on, shaded viewports add shading to the vertex coloring. When off, colors are unshaded.