Probably ought to exile it after casting; doesn't seem like a very red effect to me, but I'm probably wrong. t also doesn't include colour fixing - so it's pretty much going to be "Cast my lava axe again" isn't it?

Edit: Duh, this is the "We flipped the colour pie" set, isn't it. So yes, it's a very blue thing to get to do. The lack of colour fix is still going to be painful.

Strangely, casting things out of your opponent's graveyard has popped up on red's half of the color pie on the card Shaman's Trance. I seem to remember it happening one more time... but I can't think of what that card is.

Also, I can't see a real reason why you need to exile the card after casting. If a person has multiple Lingering Hatreds, they might as well go for it.

It seems reasonably red: a cross between Past in Flames and Fork. I agree it could be blue.