Sentence:  <WSD>Blue lights</WSD>, or blue fire, is a preparation in which zinc and sulphur, or sulphur alone, are used. The particular colour is communicated by the zinc and sulphur. 
Meaning of the word marked with <WSD> tags:  A mixture of chemicals (including nitre, sulfur and antimony) used in eighteenth and nineteenth centuries for pyrotechnics, night-time signaling and general illumination.