After installing xfce4 and xrdp the desktop colors are mixed up, with the red and blue colors swapped.
This is a really wired looking effect, which has been reported by a few people.
I’m sure it is a setting in a configuration file somewhere that has gone wrong, but I can’t find it.
A solution that has worked for me is to uninstall xrdp and reinstall it using:
sudo apt-get purge xrdp
sudo apt-get install xrdp
This will remove all xrdp customizations, so they would have to be setup again.