Actually I am pretty sure if it says the "motors resist your effort" the airlock is powered and you do not have access.
EDIT: The colony may not have power, but that areas APC may still have some. Doors are controlled by the environment circuit in an Area Power Controller, the last circuit that will be turned off as it runs out of power, after lights and equipment
If the bolts are down, it will say "the airlocks bolts prevent it from being forced".
To crowbar a door it must have no power, and the bolts up. This includes xenos prying it open
To open a door normally, it must have power, bolts must be up and your ID must have the access requirements for that door.
An airlock can only have its bolts lifted with power
An airlock can have its bolts dropped without power. Useful for stopping xenos as survivor, but without power the door will not be able to be opened again.