Well, to answer the original question, yes, it's certainly possible. The basic idea would be to drop the fence voltage across a high resistance down to something on the order of a volt. Then you'd use a comparator to turn on lights depending on what the exact voltage was. For three levels, you could use one quad comparator chip such as an LM339.
I do something similar on my utility trailer. I mounted three LEDs (red, green, amber) and each one lights up when a light subcircuit is activated. I can then just look in my rear view mirror and see that the circuits are lighting up. It tells me that power is there, but not whether the trailer's lights are actually working. Still, it's useful for telling me I got the trailer wires connected to the car.
The challenge is going to be getting the LEDs' signals visible in daylight. I'd recommend finding some high brightness LEDs, then putting them at the focus of a small converging lens (say, 10-15 mm in diameter) such that the exit beam is roughly parallel. I'd suggest experimenting with this first to find something that works. The rest of the project should be straightforward.
A different option would be to use e.g. a small FM transmitter that has just the required range. Then there'd be three different audio frequencies broadcast to code the state. You could pick up the signal with any FM radio.