I used purple because it is the opposite color as yellow. The purple loads more yellow into the petals and makes them more vibrant. Sort of like a series of black lines on a white background tend to vibrate. Because the stamen selections were deleted the purple of the background show through. In the second installment I hinted that you could use a selection to create individual selections of the same size and shape.
Lets take a look at a simple example.
Creating a selection and the moving it. In the above example I created an oval selection and used it, by right clicking using the mover tool, to copy and paste, as a new image, each of the girls in the original photo. The individual selections pasted as new selections. In the above examples, I applied a faded edge mask. I didn't wanted to lose the crispness of the edge, I just wanted to push the background away from the faces.