It wasn't white spandex in the show. That is just the cheap way people go to save time/effort.
Well, no-one I've seen has "actually" used spandex.
For instance in the pictures above, everyone is wearing white pants. Probably bought from a thrift store :wacko
Personally, and here me out on this, because I work in a fabric store with the largest 'in-store' selection of stretch material in the South-East... *ahem*.
Lycra is an excellent material for the under-suit, however... the 'issue' is how it should be approached and made. The undersuits on the show are skin-tight, flexible, and have raised details. Trying to make an undersuit as seen would be nigh impossible to sculpt and cast while keeping the same amount of flexibility and breath-ability you'd hope for a costume like that (thinking predator suits here..)
Vinyl would be a good looking alternative, but show me one that can stretch and be comfortable and I'll eat my words.
Now, If you're thinking about some-one going out to wal-mart and buying a white zyflex top and bottom, or purchasing a 'zentai suit' off of Ebay, yes. I see where you're coming from...
But isn't the point to make everything from the ground up? Find the "right Lycra" (White:brushed cotton lycra IMO) and make the pattern from scratch, If you add foam padding to create the 'tiered' effect in the armor... you'll be cookin.