Thanks for comfirmimg that the flowers are lemon / pale yellow and not white.
The reason for asking is that I have recently germinated seed of this form, which came from Dehert via the Aymeric de Barmon seed list.
Perhaps the more correct name should be fa. lutea ( yellow ) or even aff. L 1055, yellow flower has these plants must have derived from Lau's original introduction in about 1975/76 ( Huitzilopochtlia No 3, pages 19/20 )