I chose this color for my naturally very dark brown hair, based on the swatches shown on the side of the box, not the picture on the front. This appears to be a rather bright red according to the picture on the front, and it probably is on someone with medium toned or lighter hair. Using this color on dark hair will never give you the shade on the box. I wanted a suggestion of a deep red shade that did not look burgundy, as so many deeper reds tend to look on me, so I chose this over a deeper red. I wasn't expecting a huge change in hair color, just a tint. It turned out a bit more vibrant than I was expecting but I was very happy with the result. I was only expecting the red to be visible under bright lights at certain angles or in the sun, but it was visible all the time, even under fluorescents. Because my hair is so dark, this did not make me a redhead. It made me a brunette with a warm reddish tone. I got lots of compliments and even did the color a second time. The color fades and washes out slowly over time so the root line isn't terribly obvious. I'm not sure if I would do this again but it was a nice change while it lasted.
I bought this hair color because I had lightened my dark brown hair, and it ended up a orange-copper shade. I figured I would go red for a bit, and Natural Instincts has usually worked well for me. While I anticipated the color would be darker and warmer than the box indicates, I was not expecting to have an almost Manic Panic shade of red. This is NOT a natural looking red. While I actually like the punky color I ended up with, I would imagine it wouldn't be everyone's cup of tea, especially if you are looking for a natural red result. I do think my result was due in part to my starting color being already reddish-orange, but I would still avoid this unless you have relatively dark hair that you want a red tint to. I will post a picture of my results after I style it up, and I'll add/edit my review after I see it "finished". :)
UPDATE: It was a bit warm today, and even after rinsing as much as I could, I had some hair color "bleed" when I got a little sweaty. I love the color even more after styling (and I am still working on posting a pic), but it is even MORE dramatic when dry.
UPDATE 2: After waiting about 48 hours to wash with shampoo (box recommends 24 hours), I noticed a LOT of color bleed in the shower. The color hasn't faded much, though, so I'm still pleased. The picture I added shows the color in somewhat low light, so you can't see the full effect of just how bright this color is. I still love it, though, and you can't beat the shine you get with any Natural Instincts color! :)
FINAL UPDATE: I noticed after a few washings that the top few inches (the mostly virgin hair) is BRIGHT ORANGE, while the rest of my hair has faded to a light reddish brown. I take back all my love for this color, and I'm going to try a brown shade to try and tone down the Ronald McDonald freakshow I have hanging out on top of my head. Not cool, Natural Instincts. Not cool.