MTG. Can I sacrifice 3 triskelivus tokens to kill 8 1/2 tails before he gives them protection ?

He has a non summoning sick 8 1/2 tails. I have 3 triskelivus tokens in play with triskelivus still in play. Can I sac them to kill 8/12 tails. My opponent says he can make the tokens white before I sac them and add the ability white to deal 1 damage to a creature or player to the stack. He then says he can use 8 1/2 tails other ability to give 8 and 1/2 tails protection from white preventing the damage I would deal. He has ample mana open to do this over three times and says he can respond each time to make them white before I can do them. He is saying that paying a cost uses the stack and can change the color before I pay the cost of sacrifices the triskelivus toke.