Can't tag images on drone docker build: Error parsing reference: ":latest" is not a valid repository/tag: invalid reference format
Somewhere from your yml file tag value is set to empty but the docker tag command have : in command.
See the image to generate the above error.
I did not work with drone.io but there is an indentation or configuration issue in your yml file, tags under setting, so which should be like
kind: pipelinename: defaultsteps:- name: docker image: plugins/docker settings: username: kevinbacon password: pa55word repo: foo/bar tags: latest