And this image came from a slide. Both seem red to me. I wrote Graham and asked him what that meant. In most species and hybrids, the nectaries are tubular. They may be colored, but they are small and almost hidden.
Double flowers occur when the nectaries extend and become flattened, looking like sepals.
As you can see, this extension of the nectaries takes different forms. These still show a bit of their normal tubular shape - quite nifty, I think. Doubles can vary in form, too. This pink, fading with age to green, reminds me of my rugosa roses a bit. For some reason, this also reminds me of apple blossoms.