You can use whatever the heck you want but anything with ruby tinted eyes is not going to show as BEW. REW has been used to improve the type (shape) of BEW but all rabbits that also come out REW are not useful unless they continue improving the type for breeding. Since REW is recessive and can be carried without knowing it you have a very hard time ever being sure you have bred it back out of the resulting BEW or vienna marked rabbits. That may make others not want to buy any BEW with REW in it's background so while the rabbits that don't come out REW may show better they still may not have the same market as rabbits that never had the REW gene added to the line.
BEW sometimes causes stray white marks or less frequently bluish eyes without the white. Those are called vienna marked. It doesn't always occur but is a guarantee you have a BEW or vienna carrying rabbit that can produce BEW with another rabbit that carries vienna or is visibly BEW.
REW crossed to anything else results in no sign of REW unless the other rabbit has a REW gene. It does also cause related genes of chinchilla, sable, or himi to show up if the rabbit has a gene for those with a gene for REW but the rabbit will be whatever of those colors it has instead. Any odd markings are the result of other color genes.