Having just installed xserver-xorg with fluxbox, colours were displayed incorrectly and some applications were having trouble finding colours (same as above, cannot find black etc). Creating a legacy symlink in /usr/X11R6/lib/X11/rgb.txt to /etc/X11/rgb.txt fixed the problem though. Confusing though since this report has been closed, can the symlink be added to the package or is this not the underlying problem?