Songfacts®:

• Chvrches saw this track as pivotal to nailing the sonics they were after on their Every Open Eye album. "'Clearest Blue' was the 17th song we wrote, and it sort of informed the rest of the production," Martin Doherty of the band told NME. "To me it came to define how the rest sounds. When asked what he meant, Doherty replied "Well, it's big and happy and sad and a banger."
  
  "It's sort of cry-dance," vocalist Lauren Mayberry added.
• Chvrches debuted the song at the Ottawa Bluesfest on July 15 2015, performing two other previously unheard Every Open Eye tracks as well, "Make Them Gold" and lead single "Leave A Trace."
• The Every Open Eye album title is a line from this song.
  
  Just another time we're caught inside
  Every open eye
  Holding on tightly to the sides
  Never quite learning why
  
  Chvrches' Iain Cook explained to HMV.com why the band decided the lyric summed up the record. "We've had a mad couple of years and at times it's been kind of overwhelming, it's been great, but exhausting," he said. "We like the duality of that line, it's not necessarily a negative thing and not necessarily a positive thing."
• Martin Doherty recalled the writing of the song to FMQB: "We kept trying and trying and trying to pull it back and pull it back and pull it back. We originally didn't intend for this to be sort of a festival banger song."
  
  "It started out super, super low key and it just wanted to come alive. It became clear that the whole thing was building to that crescendo, the way the meter of the melody works, it's really frantic and quite anxious."
  
  "That release is my favorite moment on the record. I think it's just Chvrches in a bottle, that 8 bars and that explosion. That's what we do."
• The song plays during the party scene in episode 3 of Netflix's Heartstopper. Thanks to exposure in the hit show, "Clearest Blue" got a 522% lift in sales in the UK the following week.