This suggestion is just for us users' convenience:
We frequently press cmd + H in Mac or Ctrl + H in Windows to hide the marching ants of the selected area. However, it is quite often that we forget there's an active selection and waste time trying to find out what is on earth happening that I can't use the clone stamp or an area outside the selection.
It may be a good idea therefore to make PS warn us that the selection is active but hidden. This may be achieved by changing the colour of the tools menu when the selection is hidden, or any other visual effect to warn us to deselect the selection, once we're done with it.
Thank you and keep up the good work.
Yes - I think things have changed now that we have a lot of unused extra space, at the top of the interface area, in either the 'Application bar' or 'Options bar'. It would be possible to include an indicator of some sort in these areas saying "area selected" or "no selection active". Indeed at the far right of the Options bar there is a gray strip that is not used for anything for the last several versions. I always thought there was something in store for this area, but they decided to introduce the 'Application Bar' - a completely new toolbar for some reason instead.
Your suggestion of color coding the tools bar would also work visually. I'm not sure how that would work practically so well because it would mean a redraw of the interface each time a selection was made or dropped, and this would slow things down.