View with 2 taxonomy term in url
Set the path to:

cars/%taxonomy_term/%taxonomy_term


Then add two relations in the advanced section:

Taxonomy term referenced from field_brand
Taxonomy term referenced from field_color


Then add two times the following context filter: 

Name (Taxonomy Term)


Select in the first context filter the relationship field_brand and in the second context filter the field_color:

now it should work as expected.