Changing the colour of a select boundary in the same layer

I'm hoping this makes sense, and I've spent so much time trying to figure this out but can't seem to.

These two areas are in the same layer, but I would like to be able to change the colour of one of the boundaries, but in the settings, it's only allowing me to change the colour of both (the entire layer). Is there a way to just edit one boundary?

I'd like to change Nunavuk to a different colour than Nunatsiavut.