From the first pic it looks to have golden undertones. In order to get it back to your original color you'll likely want to go with something that has "cool" or "ash" in the title. Keep in mind, however, that when putting color on top of color it will not come out exactly like the picture on the box/swatch.
Now, keep in mind, I'm a newbie and these are just my best guesses. I'd definitely wait till some of the more experienced members weigh in. Also, since you used a demi rather than an outright permanent color it may be possible to get it back or close to your natural color by natural means, but again, I'm not sure.
Speaking as someone who has had many a haircolor come out wrong, I hope it works out for you. I'll keep my fingers crossed for you.