Many variegated plants respond to different amounts of light with alteration in the variegation, either more or less distinct, or even by covering more or less of the leaf. Finding the sweet spot where you think it looks best is the fun part, IMO. I haven't had a variegated spider in decades so not much to say about them, but many variegated plants can definitely revert and begin making plain green foliage. Vinca vine is the first that comes to mind. I've also seen Polemonium and Tradescantia fluminensis do this. Various variegations are caused by a variety of factors, some stable, some not.
