White Crops for Printouts with dark backgrounds

This is a simple yet time saving and necessary improvement.
I cant believe more people have not pointed this one out. It is very hard to see crops if there is a dark back ground. It would be nice to have white crops behind the black crops, like Adobe does, so you can see it on either white or dark backgrounds. That way I don't have to spend time creating crops by had so it will be visible for trimming down the job. PLEASE this would really help!