Not colors, terminals but on average it is the color connected to the corresponding terminal.
Terminal/ wire color
G-green wire (fan)
W-white wire (heat)
Y-blue wire (cooling) -had you had a yellow wire that may also (instead of blue) have been used for Y/cooling
R-red wire (24 volts.power)
Many times the blue is used as a common on digital stats but again, you'd have a different color wire, mostly yellow, connected to the Y terminal for cooling.
Terminal/ wire color
G-green wire (fan)
W-white wire (heat)
Y-blue wire (cooling) -had you had a yellow wire that may also (instead of blue) have been used for Y/cooling
R-red wire (24 volts.power)
Many times the blue is used as a common on digital stats but again, you'd have a different color wire, mostly yellow, connected to the Y terminal for cooling.