To animate VertexPositionColor [], all you really need to do is change the elements of the array correctly and then use the new values ββin the DrawUserPrimitives () call.
For example, in the update method of your game:
for ( int index = 0; index < vertices.Length; ++index ) { vertices[ index ].Color *= (float)System.Math.Sin( gameTime.ElapsedGameTime.Seconds / 60 ); }
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