rbailleu,
Under ideal laboratory conditions you may come to color faster with violet. In my experiences there was no discernible difference. The violet plates are extremely sensitive, the slightest variation in processor or press chemistry seemed to set them astray (which means every cleaning cycle, which is at a minimum monthly). As far as fountain solution goes I would contact the plate specialist with whomever's plate you decide to go with and contact a technical representative with your ink vendor as to what fountain solution they suggest. I've been through a few fountain-solution change overs that did NOT go smoothly at all.
Marko,
I've got a whole set of purple clothes. We called our Prosetter's processor the rabid old man as he was incontinent, foaming at the mouth and extremely temperamental.