Blue devil and Pink elephants

Blue devil noun - A coarse prickly European weed with spikes of blue flowers; naturalized in United States.

Pink elephants and blue devil are semantically related. in depression topic. In some cases you can use "Pink elephants" instead a noun phrase "Blue devil".

Pink elephants noun - Any visual hallucination arising from heavy drinking.

Blue devil and pink elephants are semantically related. Sometimes you can replace phrase "Blue devil" with "Pink elephants", this phrases are similar.