In addition to the black background frame and the colored titlebar the "tabstrip" window decoration also has an outline, which is currently hard-coded as white. This doesn't fit very well in certain color combinations, especially in dark setups, so it is desirable to make this color configurable. The idea has been ACK'ed by the tabstrip authors (Jorge MATA: "I think it would be a good idea to have a color chooser in the decoration configuration for this setting." and Lucas MURRAY: "Lovely").

The config dialog (attached screenshot) isn't particularly pleasing, but I found it hard to align the three different widgets in a meaningful way. The first screenshot shows the deco with grouped windows and black as outline color. You can see that the title bar composition doesn't become unclear if the outline is invisible, even in grouped mode. The second screenshot shows windows with different combinations copied together as an illustration. The top row corresponds to the currently hardcoded outline color white.