Vray override Material shadow color

Hi all,
Can anyone tell me how to get the shadow cast to be a different color (say red) than the material beneath, with the vray override material?
I put a vray material that’s red in the shadow slot and the shadow is unaffected.
The reflection and refraction slots work fine. Is there something else I need to do?

thanks!

J

Here is one quick example:

scene: http://ftp.chaosgroup.com/support/scenes/override\_shadow.max