Disable multi-colour marker for multi-category posts

This issue was discussed in https://www.ads-software.com/support/topic/geo-mashup-colors-on-map?replies=6

but unfortunately the link to the solution is no longer working:
https://wiki.geo-mashup.org/guides/disable-multiple-category-marker

I would like to be able to disable the multi-colour marker and simply specify one of the single colour markers for use when a post has multiple categories. Any help or an updated link would be greatly appreciated.

https://www.ads-software.com/plugins/geo-mashup/