IMO paint grenades rarely do what they are designed to do and are quite expensive. You'll have a much better chance of eliminating someone by shooting $5.00 of paint at them than by throwing a paint grenade at them.
Paint mines can work, but you have to be able to set them up in the field prior to the start of the game. often times that isn't possible. again your probably better off spraying paint than using a mine.
oh and I'd go with a Tippman too, if u r just starting out and planning to play woods exclusively.