Change 'black bars'? (Constrain Aspect Ratio Adjustments or Alternatives?)

I’m currently using the constrain aspect ratio option for an orthographic camera and need to either change the colour of the black bars or remove them (it would also work for me if there was some other method of replicating the scaling effect of this option but without the screen cut off, be it through another option or blueprinting).

Alternatively, is it instead possible to set constraint aspect ratio to work vertically instead of horizontally?

Many thanks in advance.