One of the challenges in completing this curve is to disassociate the brightness generated by the exposure from that of the colour. The red in the second from the left image is overexposed slightly and so looks bright, however, the base colour is darker than a yellow or a light green. In most of these photos the Sun was high in the sky as I tried to back light the leaves and so the colour of incident light should be fairly neutral. Had I taken these early or late in the day the reddening of the sunlight would have changed both colour and brightness.
Currently in mid-winter the Sun is low in the sky nearly all the day and so I am seeing a slight reddening of skin tones in any portraits that I take outdoors.