Would it be possible to change the line style of the outline box for both "Selected Region" and "Fixed Region" captures from the red/white dashed line to a solid black or red line? It wouldn't hurt if if it was a hair thicker as well.
Having the line color dynamically invert from red on white backgrounds to a lighter color on darker backgrounds would be even better than a fixed color on all backgrounds. This dynamic line color selection is how fixed region selection works on FastSone Viewer.
The white and dashed line works well on dark backgrounds, but not as well on light backgrounds. The majority of my captures are light or white backgrounds and the lines somtimes are hard to distinguish during the capture.