What can he to to his teeth?

my husbands teeth arent looking so great. he does a whole lot of dip... like 4 or 5 tins per day and i think that is causing his lower teeth to turn greenish yellow. he wont cut back. he loves packing a mad lip or a horseshoe as he calls it. the stuff keeps him calm and he loves it like i like cigarettes so dont say quit cause it wont happen!!!! but what can we do about the tooth color?? i got him some whitening gel and it just dont work!!!!