It would be nice if there was an option to select a different color (or some other way to make them stand out) for buttons of iconified (minimized) windows. Right now they look the same as simply inactive windows. True, this is the case for most panels out there, but IceWM inbuilt panel and tint2 do have the possibility to make iconified windows look different from both the active window and inactive ones. Yes, I know that iconified windows in window-buttons of xfce4-panel have opaque icons. But first, it's not a very distinctive feature (especially in some icon themes), and second, there is an option to display only text in window buttons - and then there is no indication at all (since there is no icon on a button) of whether a window is iconified or simply inactive. Since "window-buttons" does display icons opaque on the buttons of iconified windows, I guess internally differentiation between iconified and inactive windows is implemented. So it should not be too hard to make them more different in appearance, but it would greatly improve usability (imho).
Created attachment 7520 Screenshot of the panel This has been fixed in 4.13.2 by allowing the labels to have a dimmed color (see the screenshot attached, there's an active, an inactive and an iconified window). I presume this is what you're reporting, hence I'm closing this report. If I'm mistaken feel free to reopen.