I have never heard of a shampoo that darkens hair. I have, however, seen/used a shampoo that is supposed to help maintain color. It was meant for brown hair, but the color of the shampoo was purple (weird), and it was really hard to use since it stained everything. I only used it a few times and saw no difference in my hair.
I don't think they make that kind of stuff really... at least nothing that works effectively. The Dove shampoos are meant for color treated hair, they won't darken/lighten your natural hair. Basically they're just meant to help maintain the color you dyed your hair with.
If you don't want to dye your hair permanently, you could always dye it with temporary or semi-permanent dyes which won't damage your natural color, and wash out between 2-16 shampoos (depending on which one you use).
I would try a color depositing shampoo that is close to your shade of hair. If it's anything too much darker it may not look good when done this way. I haven't used them, but look them up online to see which brands there are.
Also, there is the John Frieda Luminous Color Glaze.. you use it in the shower and I know they make one for a lighter brown color or a darker one. It's kind of like a very weak dye and makes your color richer with use.
I have brown hair but would like it to appear darker and I don't want to dye it. Is there a shampoo that can do this for me? What about Dove's Advanced Colour Care Shampoo? Any other suggestions?
I'm not sure if this would apply to you because you have brown hair, but maybe a similar product can help you.
I have dark blonde / light brown hair that I highlight, and in the summertime my hair gets extremely light from the sun. About once a week, I used the generic Clairol Shimmering Lights shampoo. It's marketed for people with blonde or gray hair to take away the brassiness. But I find it made my hair slightly darker--more of a sandy blonde than a bright shiny blonde.
Maybe a similar product is sold for brunettes? Ask your hairdresser, or the clerk at a local beauty supply store (like Sally's).
You can temporary darken hair with Tressa Watercolor shampoo or Artec Colorline shampoo. Both can be found at Spiral Haircase! You can find it at http://www.spiralhaircase.com
I would usually suggest using it 3 times a week to start with and your hair will gradually darken. Once the desired color is reached, once or twice a week should keep it where you like it providing you don't use a harsh shampoo that would strip it out again.
The only brand of shampoo and they also have conditioner that noticeaby darkens my hair is ArtTec brand available at most beauty supply stores but not Sally's, it seems.
I would suggest the Coco Bean. It's the darkest one but since this is just shampoo which only sits on the hair for a few seconds it probably wouldn't be that dramatic. Not unless you used the conditioner, too. But again, it's not nearly the same as getting your hair saturated with concentrated permanent or semi-perm color for 20-30 minutes.