The softest colour temperature. A warm white light will have a warm, yellowish glow reminiscent of reading under an older incandescent style bulb.
The optimum colour temperature for reading under. For the Alex light, this is the closest colour temperature to daylight.
This is the recommended option and most popular choice.
The most intense white colour temperature. This option will have a bluish tint to the light output and is similar to the light given off by fluorescent tubes.