First let me mention that my cat food of choice is Purina Naturals. The first ingredient is chicken meal, and there are no artificial colors. The greenish-brown color of the food probably comes from the dried spinach and parsley flakes that are added. So, I can say that my cats 'Eat green!' Cool.
But, to get to the frugal part of the story, I have had a hard time finding coupons for Purina that include Naturals. If you'd like, you can try your local coupon-sharing Meetup groups, but I am short of time to 'network' for coupons!
Searching online for 'Purina Naturals coupons' I happened across an ebay auction for those and lots of other kinds of coupons. For those of us using a boatload of pet-related products, these auctions are a godsend. I'm bidding on a batch of Purina coupons (good on any cat or kitten chow) right now, and expect to receive 20 of them for .99, with .42 shipping. I'll save $20 using the coupons. That is well worth the hour or so it takes me to find the auction, bid on it and pay using paypal. This morning I opened an envelope of 20 coupons for Cats Pride cat litter. Each one is good for $1 off a jug of the litter, and I will probably use all 20 of them. When buying coupons, check the seller's other auctions for coupons you would like to add to your order. Usually they will combine shipping, which is often the price of a first-class stamp, and sometimes is free!
Happy ebaying, frugal friends!