Changing wall colors

[maelias@shaw.ca]

I am currently designing a duplex. In all but 3 rooms of one side of the duplex that are adjoined to the dividing wall, I am able to change the wall colors independentlly as they are attached to the exterior of the wall. When I click on the major interior wall that separates the two sides, the color goes through to the walls of the rooms that are parallel to it. How can I get the walls in each room to stay the color that I want against this one long dividing the duplex. I don't beleive that it has anything to do with the fact that it divides it but please let me know if I'm missing a secret. Thanks Mary Anne