Thermocouples wiring colors are standardized, for the K type it is yellow-red.
Also, since the metals in the wire are not copper, but chromel/alumel pairs, the wire is significantly stiffer than copper.
UPDATE: Yeap, it was a thermistor not a thermocouple. I can pick up the change in resistance with arduino but thank you for all the thermocouple suggestions (ans sorry for the confusion)