At the moment of anthesis (opening) the petals of a Wahlenbergia thunbergiana flower are pale and brown-veined on the outside, faintly red at their tips.

Once they part, the whiter inside surfaces are revealed. Recurving of the upper halves of the petals starts straight away after separating on the plant in picture, less so in some plants of the species (Le Roux, et al, 2005; iNaturalist).