This would be a nice feature, definitely, in fact I wish the NPC outfits made available were dyeable (I don't want to cosplay as that specific npc, SE! I just want that jacket!). However, in SE's defense, this is why I check to see the gallery they make available for an item to show what a mogshop outfit looks like when dyed. Both the carbuncle outfits provide a dyed preview on their respective pages. That said, it would be nice to have a ruby carbuncle option for these outfits.