The chameleon came into my head when I thought about change. They are amazing lizards. Apparently they have both brown skin cells and green skin cells. When they are standing on a brown tree trunk, they dilate the brown cells (so they look brown) and contract the green ones (so the green skin can't be seen). When they are standing on a green leaf, they dilate the green cells and contract the brown ones. We saw some in Malaysia when we went there a few years ago.
I did a pen and ink drawing and then went a bit crazy with Photoshop and some coloured pencils.