Question
i transplanted a cardinal flower with red flowers last year this year they had white blooms what caused the change i have clay soil i added peat and tilled it into the soil  

Answer
Soil pH has nothing to do with it in this case.  My best guess is that your red-flowering plant died and the one with white flowers is a volunteer seedling of it.  Many native plants will frequently produce white-flowered offspring.  I have never heard of a plant actually changing the color of its flowers and consider that extremely unlikely if not impossible.