[Filling in areas with black border reversal issues.]

I set the tolerance setting to 0% and that appeared to help, but it still tinted the borders.

 

Using the magic wand tool before changing the colour of an area appears to have fixed this somehow. The area highlighted no longer affects the border colour anymore so long as I select the area before hand.

[Filling in areas with black border reversal issues.]

I have been having issues while making a basic bordered map. It is a simple 2D world map with black borders, a blue sea and plain white areas representing different regions. I noticed that when I filled in one of these 'regions' with a colour (red) and then tried to refill that area with a different colour, I ended up tinting the normally completely black borders. I've tried messing around with some of the settings that I am familiar with and I have looked for people having similar issues, but I have not found any solutions as of yet.