Coding force sensitive resistor to give output based on time used?
You'll need to declare a variable to hold the start time (millis()) of when the force has exceeded the threshold.

You'll need to declare a constant to hold the threshold value (with analog data, you likely don't want to have your pressure threshold be "anything greater than 0", because noise and other things like small vibrations will trigger.

Also declare a constant to hold your "hold-off time" in milliseconds.

In your loop(), when you have an analog value that exceeds the pressure threshold, store the value of millis(). Also in your loop(), when the current millis() minus the start value  is greater than the "hold-off time", activate your LED.

For RGB, same setup, but you can set your color based on how much greater the time difference is than the hold-off time.