How to: Wire aftermarket fogs to OEM wires/switch
**Warning, I know nothing about electricity, OHM's law or any of that crap. I'm just trying to help out the next poor sap.**
I bought the Spyder kit and the OEM turn signal from amazon (~$200 shipped) for my 2013 skyactiv hatch. Getting the bottom of the new light housing to snap into place was a major PITA, and I didn't get it all the way in. Whatever.
The fog light kit came with a wiring harness, relay and a switch. I didn't want the hassle of running wires through the firewall, so I decided to use the wiring already in place from Mazda. I couldn't find a matching plug, so I cut the OEM harness off (someday I'll find the matching half and do it right; for now, I hard spliced them to wires).
I undid the harness, and separated the junk I didn't need. then I messed with the relay for a while and couldn't get it figured out. The relay wasn't the standard foglight relay, so I sh*t canned it, and got a regular fog light relay with numbered prongs (same kind on my Hella's) for $5 at the auto parts store.
The factory plug on the passenger side has four wires:
Orange (constant power),
Green (switch), and
Gray (switched power)
Connect the Orange OEM wire to relay post 
Connect Green OEM wire to post 
Connect Gray OEM wire to post 
Connect Power wire (red) from foglights to post 
Connect Black OEM wire to ground wire on foglights
That's it. Your aftermarket lights work with your factory wiring and switch. No drilling, no holes in the firewall, no janky aftermarket switch...easy.
While messing with it, I also found that if you don't connect the Green OEM wire, your foglights will come on with the parking lights (the fog switch doesn't work). I don't know if this might be a workaround for the mod that so many people do, but I considered running them like that instead.