I've been using joe for years and just discovered the potential for syntax highlighting. I can turn it on by pressing ctrl-t, moving to the highlighting option and pressing the space bar. [Enter] then closes the options. But, when I then load a .c file, there is no highlighting visible.
The editor is launched within a virtual terminal (rxvt) with a black background and light grey foreground. I don't mind playing with colors in ~/.joe/syntax/c.jsf, but I haven't yet figured out how to 1) have the highlighting work on a file and 2) set this on permanently.
Most likely you already have a $HOME/.joerc from a previous version which is not set up to do syntax highlighting. Delete (or rename) it, so that the system default file is used.