Version: (using KDE 4.4.0) OS: Linux Installed from: Ubuntu Packages Kopete styles use hard-coded background color for chat schemes (i.e., 'background: white' or 'background: $FFFFFF'). I believe it is not necessary because using system-wide light-color background is fine. Please remove hard-coded background for body in CSS files. Another case is to add variants without background color to use system-wide background color.
Dear user, unfortunately Kopete is no longer maintained. Please migrate to another solution, e.g. for Jabber a possibility is Kaidan, for Matrix a candidate is NeoChat.