The wire colour alone is not enough to determine where it needs to be connected.
If you've not already done so I'd recommend checking your system is compatible:
Nest thermostat compatibility - Google Nest Help
Once you've checked that, use the correct app for setup. Use the Nest app for Nest Learning Thermostat and Nest Thermostat E models. Use the Google Home app for Nest Thermostat (2020 model). The app will guide you through the setup and tell you where to connect the wires.
