How to delete SOLR indexed data by query with curl?

Using JSON instead of XML:

curl -g "http://localhost:8983/solr/$core/update" \
     -H 'Content-Type: application/json' \
     -d '{"delete":{"query":"field:value"}}'

You have to add query tag.

<delete><query>(cartype:stationwagon)AND(color:blue)</query></delete>

In this way would be easier:

curl -g "http://localhost:8983/solr/collection/update" \
     -d '<delete><query>(cartype:stationwagon)AND(color:blue)</query></delete>'

curl "http://localhost:8983/solr/collection/update?commit=true"

It's a simple POST request.