3 way wire dimmer question

If electrical work was as easy as connecting matching color wires together my job would be a lot easier.

The old 3-way switch that you removed had three screw terminals on it. Two of those terminals were of the same color and the third was a different color such as black or red. The wire from the odd terminal is the one that should have been put on the black wire of the 3-way dimmer. It seems that one of the red wires in the wall box is what gets connected to the black wire of the dimmer. Connect the black wire from the box to one of the red wires on the dimmer and forget about it. Now connect one of the red wires from the box to the black wire on the dimmer and then connect the remaining red wire from the box to the remaining red wire on the dimmer. Try it out. If that doesn't work reverse the red wires. If it still doesn't work, post back and we'll have to identify each wire and start over.

The wire in the wall box that goes to the black wire on the dimmer is the important one.

The one that is on the black wire now is not it.

Try one of the other ones. If it doesn't work then the last one has to be it.