It is not the plant from the photos, and your description settles it. Green with silver marbling on top and purple undersides is the standard Ceropegia woodii, and that is exactly what it is supposed to look like. It does not turn pink. No amount of light will do it.
The pink one is sold as variegated, often labelled Variegata, and it has cream or white or pink edges on the leaves and pink stems. That is what the photos are. Yours is healthy and doing its job.