Golelorn has got it correct above that if per Vertex colour is stored in the 3d object that it is passed to the vertex shader as:
attribute mediump vec4
color; <-- Per vertex colour information stored in the model
Most objects dont have per vertex colour unless you specifically try to create and save it in your 3d editor.
vec4 agk_MeshDiffuse = The color of the mesh being drawn, set with SetObjectColor
vec4 agk_MeshEmmisive = The emissive color of the mesh being drawn, set with SetObjectColorEmissive
In addition to these SetAmbientColor() sets the minimum amount of light an object receives.
