They're used in things such as Tv set remotes to mail tiny parts of knowledge in the form of invisible light! These may appear to be typical LEDs so It will likely be really hard to distinguish from ordinary LEDs. The wavelength of light, and therefore the colour, will depend https://www.infouflo.edu.ar/php/news/ir_hacia.php?what=2016-11-30-13-42-12&dtn=[RCPT_EMAIL]&voyhacia=https://newzlight.com/