Unnaturally Blue Lighting

"I used to like the color blue. Now it's dead to me. Cram it, Smurfs. Piss off, ocean. Screw you, sky."

—Riff Trax on Battlefield Earth

A subtrope of Mood Lighting common in Science Fiction and Forensics shows. Shots are suffused with vaguely blue lighting. This is usually complemented by stark, overly bright desk lamps. Occasionally this infects outdoor scenes, making sunny days look more overcast; this should not be confused with the dark blue camera filter used in shooting "day for night".

A low-intensity version of the effect can be produced by shooting a scene light with daylight-balanced light on film (or its digital equivalent) that is balanced for incandescent (tungsten) lighting. Daylight has more blue than incandescent indoor lighting, but typically has less than some fluorescent lighting used in offices, which may be part of where the trope originated. In the early 80s, HMI-lighting (strong lights, with daylight temperature) came and was often used outside, mixed with regular bulbs, giving them a strong blue tint (as they were bluer than they are today), which is often seen in the early 80s. Today it still remains for moonlight, as otherwise it would be hard to separate from daylight, however often in a much subtler way.

Although this is a good way to cover up a lower-budget set, the light can sometimes become glaring and/or induce too many shadows.

Nowadays, the rise of Orange-Blue Contrast makes this nearly ubiquitous in mainstream movies and television.

Examples of Unnaturally Blue Lighting include:

Advertising

For whatever reason, it's being used in recent Viagra commercials like this one (maybe because the pill itself is blue?). The effect is weird because that particular commercial takes place in the desert.

Film

Used to great effect in Little Buddha, contrasting the cool blue Seattle shots with the warm reds of Tibet.
In The Lord of the Rings films, the battles at Helm's Deep and Osgiliath are shown in a blue tint.
The Underworld series makes consistent use of trope, blended with Hollywood Darkness. Individual scenes which aren't primarily blue are a rarity. Even the DVD covers invoke this.
Minority Report is a classic example—it's in most scenes and submerges some of them. Some viewers found it strained their eyes.
The future scenes in the Terminator films look like this.
The first Twilight movie had this, possibly to emphasize the characters' pale skin or the cloudiness of Forks. The sequels had more of a golden, warm tone to them.
The One uses this to distinguish between the different universes that the movie covers; the first universe plays this trope deadly straight with heavy blue lighting, the "central" universe and Gabriel's one have slightly cold lighting with a little blue, and the "happy" universe that Gabe is sent to at the end has warmer, more orange lighting.
Done in Blade 2. Daylight is a cool blue, to contrast with the harsh, halogen yellow of night lighting.
The more recent Harry Potter films use this a lot for any scene that isn't in Hogwarts, and some that are, probably to go with the Darker and Edgier direction they're trying to take the franchise.
Battlefield Earth: Most of the Psychlo-centric scenes are shot like this. It is possible they are taking their lead from the novel where Pyscho "breath-gas" has a purple tint.
In The Matrix, all the scenes that take place in said Matrix have green lighting (except for the non- remastered first film). It's computerized tinting done entirely in post-production. That's why the non-remastered version is different. Similarly, scenes set in the real world have a blue bias.
Used in Pitch Black, though it's Justified by making one of the planet's suns a blue giant and it's only blue when that sun's in the sky.
In one dream sequence of In the Mouth of Madness, Cane tells the hero his favorite color is blue. Much to his horror, the next scene is filmed with a very heavy blue tint.
Traffic does this with Michael Douglas's politician storyline. Each storyline in the film is distinguished by slightly different filters.
Justified in the second half of Melancholia, where the sky is dominated by a giant blue planet. It becomes intensely blue light when the planet is about to crush Earth.
The US remake of The Ring is filmed with a blue tint.
- Nah, that was just Seattle.

Live-Action TV

CSI
- CSI: NY used this a lot in their first season, not only in the lab but in the outside sets too. To the point where many viewers kept feeling that New-York looked cold or in perpetual twilight. In an example of good Executive Meddling, the producers were asked to tone it down in the later seasons. This and a change in sets for the lab (from cement basement to windowed skyscraper) helped the show feel less like CSI: Antarctica.
- CSI: Miami uses orange and yellow light a lot to enhance the "sunny" feel of the scenes. They are more subtle about this than CSI: NY was with the blue lighting, but it still shows, especially on sets located indoors.

One instance where this became humorous was when they had a crossover with CSI: NY, and David Caruso obviously brought his orange with him when everything else was blue. This gets a Shout-Out in the ads for the CSI Trilogy with pictures of the three leads tinted with their respective lighting. (original being green)

- The lighting used on the shows seems to extend to the DVD packaging with CSI being in green boxes, CSI: NY being in blue boxes and CSI: Miami being in—you guessed it—orange boxes.
Stargate SG-1 and its spinoff Stargate Atlantis has this in spades, the Asgard and Human spaceships especially. The Ancients get into it as well.
Battlestar Galactica: Used for most of the scenes that happen on New Caprica and the 1st Earth in the remake. In addition, the Algae Planet had a more grey-blue tint to it. Scenes in Caprica had a bad orange lighting even before the nukes hit.
Parodied on The Suite Life of Zack and Cody.

"Let's try the blue light" *yellow light comes on* "No, the blue that's not yellow."

Used in Mystery Hunters for a "creepy" effect with personal accounts.
Smallville was particularly fond of doing this in their early seasons to show contrast between Lionel's cold blue office in the urban Metropolis, compared to the golden glow of the Kent's farm home.
In the first season Superboy episode "Terror From The Blue", about corrupt police officers attempting to kill Lana Lang when she witnesses an attempted murder, the first segment of the episode has a heavy blue tint. After the first commercial break, the blue tint is gone and all colors are normal, making the blue tinted scenes particularly obvious when watched on DVD.
Used once an episode on Dark Oracle, every time the comic began influencing the real world.
Silent Witness: Unnaturally Blue Lighting is used regularly, particularly in pathology scenes. Partially this is an exercise in fashion and style: many contemporary British dramas were also using the technique. In the pathology scenes, the lighting increases the cold, clinical and confronting atmosphere.
Murphy's Law: Murphy has to infiltrate various criminal organisations, often ending up in harsh situations—emotionally and physically. These get the blue filter treatment. In "Go Ask Alice" the lighting visibly changes: from normal to starker and starker blue as Murphy discovers a whole family has been shot. There is a quick slide back into warm tones as he drives away for the next scene—which is a quiet, rural, conversational scene. The color isn't always explicable in-scene, but has assumed a life of its own, like visible background music.
Used in Instant Star in the school hallways, to disguise the fact that they're the same sets as Degrassi.

Video Games

Star Wars: X-Wing has this in the scene where a disturbing-looking medical droid is helping treat your rebel pilot's injuries if he survives his ship being destroyed and doesn't get captured by the empire.
Fallout: New Vegas: While solely not for Mood Lighting purposes, night vision abilities work this way. In particular, using cateye (potent night vision drug) in very dark places will make everything heavily blue-tinted, which does make things easier to see, at least.
In The Legend of Zelda: Skyward Sword, the Silent Realm is like this when Link isn't being chased by the Guardians.
Mass Effect is a heavy offender, going as far as giving crimson sunsets a blue halo.

Real Life

L.E.D lights (especially poor-quality ones) have more blue light in them than fluorescent lights, and the most sensitive spot on the human retina, the fovea centralis, has no blue light-detecting cones, so blue lights are much more uncomfortable for the human eye to look at. This has raised some health concerns about them, as they may disrupt humans' sleep patterns, since they suppress the production of melatonin, the sleep hormone.
- This is because most “white” LEDs are made by starting with blue emitters, then adding a layer of fluorescent compounds (“phosphors”, although not all such compounds actually contain the element phosphorus) to convert some of the blue light to the longer wavelengths. Low-grade LEDs may use less phosphors than desirable, and phosphors can also degrade causing the light to gradually turn bluer with age.