Version: rev.: 1039758 (using KDE 4.3.2) Installed from: Fedora RPMs Because the line is black and the histogram is black. Perhaps some xor would be useful so that the line would always have different color.
It seems that the line is drawn with the QPalette::Link color role and the histogram is drawn with QPalette::Foreground. So it's responsibility of the theme to provide different colors here, if this is expected so.
Created attachment 43857 [details] Change the curve color of the "Gray" theme to dark gray. With the "Gray" theme both the curve and the hystogram are black. This patch changes the curve color to dark gray.
SVN commit 1130371 by cgilles: fix curves color with Gray theme BUGS: 211804 M +1 -1 Gray WebSVN link: http://websvn.kde.org/?view=rev&revision=1130371