This tag is for images with an emmisive red light source. There must be a red light casting a red shade either on screen or offscreen. It's important that the red light is a significant portion of the image
When to use
You can clearly see where the red light comes from, like a lamp, a bright neon sign, or sunlight coming through something red.
The red light changes how the picture feels or looks a lot.
The red light is visible and a key feature of the character (like with Olimar from Pikmin)
When not to use
If there's only a little bit of red such as with sci-fi suit LEDs that doesn't change the picture much.
If the surface is red (like they're painted red or a raspberry) and not emmisive
If there is rainbow light
More than two different colored light/light sources
Exceptions
If the picture is heavily desaturated, but there's saturated red lights, you can use this tag regardless of the light size
