If I chose render to exact resolution in the render tab and key in the size I want, there is a dark shade on the top and bottom view of the camera which represent the border of the values I placed. But the shade for me is too light.

Is there a way to make it with a much darker shading so that I could see it much clearly?

Passion is anger and love combined. So if it looks angry, give it some love!

According to SmithMicro support there is no option to change the color or opacity of the overlay.
It is hardcoded in the software.
SM support did suggest changing the background color temporarily.
That doesn't help when your scene is a room or enclosed by a skydome.

You could work with a floating window matching your production size.

 

Yesterday's the past, tomorrow's the future, but today is a gift. That's why it's called the present.