The brighter red picture is a picture of a rose petal when I first got it. The next two pictures are petals from the same rose but taken 7 weeks later after the rose had been drying in my room.
The color difference is very clear between the two pedals, but it is also much easier to see and distinguish the individual cells in the dried rose. They appear to be much more transparent and more distinct from one another. My hypothesis is that it it easier to see through the cells of the dried rose because there is no longer any water or liquids left in the dried cells. this means there is less substance to stop the light from passing through.