When breeding, each parent contributes colors to the "gene" pool. The new dragon is then created from the colors contributed. There is no requirement that a color comes from each parent. So, yes, it is possible that the pink from Surprise splits into red and white and these were the colors for the new dragon. Next time you try that combo, it is possible that only the red or white is used. Or the pink doesn't split. Or the new dragon is a blue/yellow combo.