Although white marigolds have been around for years now, I do remember when the first white marigold - I think it was Snowdrift - came on the market. It took plant breeders years to isolate the white ones, then to propagate them and have them come true from seed.
This would seem to indicate that the white color is a recessive trait, and if that's the case, any crosses you make with white marigolds as one parent will most likely not be white.
That being said, marigolds self-pollinate and self-sow generously, so it should be easy to get some and give it a try. Edited to add: I did a little research in the database and other places, and all the white ones I saw listed are F1 Hybrids and will not come true from seeds. So not likely you'll get any white traits in the seedlings.
