Why would a red rose bloom on a white rose bush?

I have 3 rose bushes planted in my front yard. 2 are white and 1 is yellow. Last weekend I noticed a red rose bud on my white rose bush. There are about 15 white roses on this particular bush and now the one red bud is blooming into a beautiful rose. Does anyone have any idea why this one rose is so different?

Why would a red rose bloom on a white rose bush?
There's two possibilities. The first is that the red rose is due to spontaneous mutation in whatever founder cells gave rise to that particular branch of the tree. That's always possible, though I believe red is dominant over white, and so white is probably a loss-of-function trait and thus isn't likely to spontaneously revert to red flowers. A more likely explanation is that your plant was produced via a graft of two different types of rose plants, one red and one white. Grafting is a common technique and may result in a plant that is genetically non-uniform (including, even, different species of plant).
Reply:This is because of cross polination. The bees are going from one bush to the next and polinateing them (I may have spelled that wrong) so you can get roses of different colors because of this. We have a peach tree in our yard, and our neighbors have a different kind of peach tree in their yard and sometimes we both will get a cross of the two trees because we are the only ones on the street with them!!! I think its pretty interesting when this stuff happens!
Reply:Praise Jesus, its a miracle! Call the Vatican----
Reply:Some years back the white rose bush was probably grafted with a red rose bush, it might have taken some time for the red rose bush to "take" You should be able to have more red roses in the future