You're going to need a split line in order to restrict the colour to the overlapping region.
I think you need to create a 2d sketch on the first face, select the second face and Convert Entities. Then use the Split Line feature to split the first face. Finally, colour in the area created by the split line.
A reasonably big job to do all that in the API.
Thanks for your kindly reply.
Yes, you are right, I just want to prove if we can make it in the API, So I may try another way to acomplish it .
Very appreciate your help, thanks a lot