Actually, it is pretty hard to tell or predict the part of color of kittens you will get. However, kittens color can change as they mature and grow during their first year. The color pattern usually varies from different breeds of cats.
Either: 1. There is more than one dad 2. You have two albino kittens 3. You have two deaf kittens. Pure white cats with blue eyes are sometimes deaf. Do a hearing test on them and if you are still not sure take them to a vet.