For Brandon you can build up to the property line (as compared to on it). As long as its built to code/bylaws, if you don't pay you have no say. So if the OP paid for the fence then the neighbor had no right to paint it. Its always a good idea to talk to your neighbor, may be willing to share cost. I built a fence between myself and our neighbors and paid for it all but I talked to them first about it. Now it needs stained, I am paying for it and told them that if they want a different color on their side I was fine with doing it. Its about courtesy from both sides, like Tim and Wilson
You can get any info about fences/construction from your localplanning district, each may have different rules but here is Brandons.
http://brandonareaplanning.mb.ca/images/handouts/fence.pdf