Prewashing OBV bamboo velour?

I have some dyed and undyed bamboo velour from Little Gumnut. How should I go about prewashing it? And does the dyed fabric need prewashing as much as the undyed? Is the dyed likely to stain the undyed in the wash and therefore should I prewash them separately?
There, phew! Enough questions. Thanks for any answers.

Help?! I need to use this tomorrow so all help really appreciated.

No idea sorry, maybe try messaging Ems of Little Gumnut directly? She's on FB and on here too x

OBV does then to shrink a bit in the wash. I had assumed previously that dyed OBV had been preshrunk, but as a t-shirt I made got a size smaller after the first wash, I would say it depends on the quality of the OBV, and what the person dying it has done in their steps to get it dyed. So definately prewash your undyed OBV, and get info back about your dyed stuff. If in doubt, better to prewash once just in case.