My sons car fans wont turn on causing overheating. He brings it to me with a light switch some wiring from a trailer and said "I already cut the plug off Pops." So i now have to wire a toggle to manually turn on the fans. Plenty of videos out there but none are great with wiring. I have a black and a blue wire from one fan and a grey and white from the other fan. Which wire colors are what?

1998 what?
What are the indications that it is overheating? If this is a GM based FWD electric fan setup, low speed fan turns on at 212 and highspeed turns on at 226.

Sorry mike. It is a 1998 buick century. Son said it'* gotten almost to the redline a couple times. Which means, redlined it smokin several times , I'm sure.

Original edit. Found the part he had cut off. Wires were rubbed down a bit. True colors are yellow and grey, green and black.

Hate to ask stupid questions, but are we sure there'* sufficient coolant? What does the underside of the radiator cap look like? Milky? Is the front of the radiator clean? What is the maintenance history on this?

My money is on head gaskets. Over heating and redline/smoke.....YIKES..
Here'* the wiring diagrams.

It'* probably just a relay. It'd be worth hooking it back up correctly the fix the original issue.