Installed styles for chat are placed in:
# systemwide: $KDEDIR/share/apps/kopete/styles/ # on debian it is: /usr/share/apps/kopete/styles/ # per-user: ~/.kde/share/apps/kopete/styles
I have created a simplified variant of retropete (read and blue swapped, local sender changed to "me" etc.)
Check the boxes corresponding to the following entries:
General
Events
Chat