I am trying to replace a light switch from a dimmer to a single pole. My wires are red coming from the top, and another red wire and yellow wire coming from the side. Currently the two red wires are tied together with one of the black wires from the dimmer switch, and the yellow wire is connected to the other black wire fro the dimmer switch.

Sounds like someone bypassed a three way.
You can:
1) Connect the new switch with the 2 reds and a short piece of wire to connect to the switch(pigtail), and connect the yellow wire to the other terminal on the switch

2) Separate the 2 reds and connect to the same 2 colored screws on a 3 way switch, and the yellow to the odd screw. You will be able to switch from 2 locations again.

3) Install a 3 way dimmer and had 3 way light control with dimming.

It's not necessarily a by-passed 3-way. The reds could be a feed-thru hot, and the yellow is the switch leg. However, Strats #1) is probably the way to go. (You'll Probably see a couple of whites in the box tied together if this is the case).

This is NOT a 3-way. The dimmer only has two blacks.

The SP switch will connect to the same wires the two black dimmer wires are connected to.

sward05, are you in or around Chicago?

Stanfortyman,

I am in the Chicago area. I actually connected the two red wires together to one terminal, and the yellow to the other terminal while waiting on the first reply and it worked. Thanks for all of your suggestions.

I see now it was a red from the top and red and yellow from the side meant into the box, not on the switch, if he mentioned the whites which are likely with both of these sets of wires, I probably wouldn't have missed.
I believe there are 2 whites tied together in the box. My Mistake.