- Visible light towards the blue end of the spectrum generated from the screen of an electronic device.
- (historical, uncountable) A mixture of chemicals (including nitre, sulfur and antimony) used in eighteenth and nineteenth centuries for pyrotechnics, night-time signaling and general illumination.
- 1828, Gray, Samuel Frederick, The Operative Chemist, page 499:
- Blue lights, 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.
- 2015, Ragan, Mark K., quoting Robert Fleming, Proceedings of a Naval Court of Inquiry into the Sinking of the Housatonic, 1864, quoted in 'Confederate Saboteurs', Texas A&M University Press, →ISBN, page 98:
- When the 'Canandaigua' got astern, and was lying athwart, of the 'Housatonic,' about four ship lengths off, while I was in the fore rigging, I saw a blue light on the water just ahead of the 'Canandaigua,' and on the starboard quarter of the 'Housatonic.'
- (countable) A flashing light, usually fitted to an emergency vehicle.
- 2019 October, Roger Ford, “Power failure highlights specification confusion”, in Modern Railways, page 26:
- Until these trains could be restarted, they blocked lines out of Farringdon and King's Cross, trapping other services. Blue-light escorts were provided where possible to get engineers to the stranded GTR trains to reset the software.
- Used other than with a figurative or idiomatic meaning: see blue, light.
The original chemical mixtures burned with a blue flame. Later versions omitted any colouring agents, producing a bright white light, but retained the name by convention.
- Blue light (pyrotechnic signal) on Wikipedia.Wikipedia
- Emergency vehicle lighting on Wikipedia.Wikipedia
- To travel quickly in a police or ambulance vehicle with the lightbar (and possibly the siren) activated.
- 2011, Donoghue, John, Police, Crime & 999, Troubador Publishing, →ISBN:
- When we weren't blue lighting, we had to obey the 30 mph limit, but out of town we had a training exemption from any speed regulations and were encouraged to push the car to its limits... and we did.
- 2012, Mukand, Jon, The Man with the Bionic Brain, Chicago Review Press, →ISBN:
- They jumped into his cruiser and blue-lighted it to Boston Medical Center at eighty miles per hour.
- 2014, Rennie, James, The Operators, Pen and Sword, →ISBN:
- Roger that. Feds and green army are blue lighting to you.