Fairly self-explanatory; there should be an option in the canvas input settings, probably under "Tool Invocation", to activate a drawing tool (i.e. the brush, bucket fill, etc.) and use the selected background color instead of the foreground color without having to swap the two.

I'd use this so that the default activate would be bound on the left mouse button and the background color activate would be on the right mouse button, as I have accustomed to on other drawing programs and which is practically a necessity with pixel art; drawing pixels (with the pixel brush) would be as easy as erasing them (at least with a solid color background).

Pardon me if this has already been suggested or exists as a feature - I was not able to find anything despite trying to look for at least a couple of hours.

ok