I'm using Apache Solr with Facet API, and want to allow users to filter negatively by items that do NOT have a term.
For example, I have a Facet API block connected to my taxonomy for color:
And I want to be able to filter by items that are NOT red, or NOT blue (in addition to being able to filter by items that ARE red, or ARE blue).
Can someone point me in the direction of how to most easily achieve this kind of functionality? Is a custom widget needed? Does Lucene syntax support negative filters out of the box? Surely people have attempted this kind of negative filtering?