Joe 4.6: How do I override color definitions?

After upgrading from Debian 9 (Joe 4.4) to Debian 10 (Joe 4.6), the following lines in my joerc started creating errors:

=Preproc    yellow
=Tag    cyan bold

I used this to override the default colour scheme, which has C pre-processor lines in dark blue, which is very difficult to read when using a terminal with black background. I am unable to find documentation on how to do this in 4.6, the entire section on colours has just disappeared from the default /etc/joerc. Any help would be appreciated.