I am not sure. I have the XB Monte Carlo which is a black chasis. I also have the M03-M kit which is also black. They probably have a grey & black one to differentiate between the M03 XB and kit form.
I tried the Tamiya AW (anti wear 53439) grease in my diff last night and it really slowed up the diff action which will provide better traction when powering out of corners. You can also put an additional spacer in the diff which will tighten it even more but i have heard that this chews out Universal CV joints and it is advisable to run the normal dog bones.