pbs Digest, Vol 93, Issue 25
mhach@ix.netcom.com (Wed, 20 Oct 2010 11:22:12 PDT)

Jon-

Although I am no expert on Zantedeschia the only forms that I am aware of for Z.aethiopica are white and a pale pink called 'Marshmallow'. There are also two Dutch introductions 'Pink Mist' and 'Red Desire' which I know of only from photos that are also varying shades of pink with a colored spadix. I suspect that they are similar and not very different than 'Marshmallow'. My plants of Z. odorata have a cream/white spathe - but i wouldn't call it yellow.
I have never seen a true yellow Z.aethiopica and all the yellows come from Z.elliottiana (recognizable by the black blotch in the throat) or hybrids created through years of breeding. Calla breeding has come quite a ways with flowers now available in the full spectrum - with some even having blue tones visible in the flowers.

Marc
New Jersey USA