I noticed that with the strawberries and cherries I did loose a little color
in the fruit. They turned light pink. I stored all my batches in a dark
closet and I still noticed the discoloration of the fruit. Its all part of
the process. The flavor of the fruit comes out into the vodka thus taking
some color away from the fruit. I have never tried rum with this. If you
want to try it, get the purest white rum you can find, the less
congeners(flavor) the better. I think the whole point is that you are suppose
to be flavoring the alcohol yourself. So you want to start out with something
pretty much flavorless like vodka or everclear and add to it your own flavor
(sugar and fruit). If you add the right amount of sugar and you extract
enough of the fruit's flavor, the end product really won't taste like vodka.
I'm not sure how raspberry rum would turn out. Best of luck.