Need help replacing an old 4 wire thermostat

Hi,

My old thermostat has 4 wires, Red, Yellow, Green, and Black.

It had Red + Yellow tied together into the R slot, Green + Black tied together into the W slot.

My new thermostat has slots for: R, RC, Y, W, G, O/B.

Everywhere I look online it says that a White cable goes to the W slot. Is it possible that my Black cable is really a W one since that's where it was originally?

Thanks!

submitted by /u/thisFlash
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