The same thing will happen if you breed to Agouti. Using Agouti for an outcross in not recommended however as it tends to make the points meals and ruins the Siamese color. If you breed a Siamese to an Albino your resulting litter will be all Himalayan. Two Himalayans bred together should produce about one fourth Siamese, one half Himalayan, and one fourth Albino. If your are making Himalayans it is important to use an Albino which is out of a background of good Blacks with dark feet.
White feet are the number one problem in Siamese rats.
They can ranges from the entire hand being white to the wrist, to half the hand being white, to just some white on the toes. Any white on the feet is bad. If you must breed a Siamese to a rat with white markings, do so with the understanding that it will take a number of generations to get rid of the white feet. The best way to eliminate white from the feet is to outcross to a really good Self Black which has pigment all the way down to it's toenails. A good Black is also an excellent choice for darkening the oints and improving the shading,though simple selection also works well.