What colors do cats see?

Lotta google hits on that.

I did Google, Bing and looked at the images. From what I read she should not be able to tell the difference up close, 3 ft or so when I give them to her.

May be just smell, no big deal, I was just curious.

It may be the flavor of the treat, rather than the bag. Are they beef? My cats always liked fish or chicken better than beef. You could try a switch and put some of the declined treats in a different bag and see if it makes a difference. If so, that's one really discriminating kitty!

I started feeding Zia treats.. she sometimes won't eat anything else. Must be like candy for them.

Only way to know that is be a cat!

Cats do not see colors in the same vibrant way we do, red is particularly subdued. They are not color blind and can distinguish between colors, but red will not look as vibrant or exciting as purple. In fact, cats dogs and many other mammals have recently been found to see into ultra violet, a whole world we cannot see! They also do not see well past 20ft and do not see detail like humans, but they see in dim light and detect motion in low light much better than us. My cats are not big fans of beef either, my guess is kitty has associated the red bag with a flavor she doesn't like and purple with her favorite. Likely if you swapped the treats in the bags she would quickly associate the treats she likes with whatever bag you put them in.

http://www.wired.com/2013/10/cats-eye-view/

Cool question!

So, finish the product in the purple bag. Save the bag. Then take the product from the red bag and put it in the purple bag. See if cat cares.

I think it is the scent, not the bag. But then, I'm a cool cat. Some cats are not as cool as me.