Created attachment 107653 [details]
Status quo

With an Icons-Only Task Manager, running programs are distinguished with a light gray line that changes to light blue for the active program. This is an extremely subtle visual effect that strains the eyes to look for, and doesn't provide at-a-glance indication of which programs are running.

A less subtle effect may be beneficial here to. A more obvious but still acceptably visually pleasing effect would be to instead of drawing a thin colored line, use that same color for the background behind the program's icon (this would require using a different effect for when all of all of a program's icons are minimized).

I've attached two screenshots: one that shows the status quo, and another that shows a mockup of the proposal.