New Redemption Grab Bag now includes an assortment of 500 cards from five (5) different expansion sets. Available at Cactus website.
Some thoughts I have are that you can always look either on Lackey or the resources section in Land of Redemption to get the brigade information for any card. Then you can build decks accordingly. And for playing casually, perhaps you can just write on the front of the card sleeve what each card's brigade is. For tournaments I'm not sure if that's allowed, but if not you could just get to know your deck's cards well enough that you can memorize their brigade. And you can always ask your opponent what brigade any of their cards are if they're playing any you don't already know.
Just Adobe Reader (which is free). I would recommend though using the Excel spreadsheet of every Redemption card on this page (the direct link is here). LoR has some really helpful resources!Also, on Your Turn Games' website, you can sort/filter all the individual cards in the game by brigade (amongst other factors). Just go to Buy Redemption CCG --> Singles and then use the Filter on the left. Then you can see images of all the cards matching that filter. For example, here is all the black brigade cards in the game.
Maybe in future sets there could be a short identifier in the corner next to the set symbol? Just one or two letters should be enough.