Light bulb manufacturers like GE,Phillips sell bulbs as soft white and cool white. the soft white bulbs emits yellow light actually.and the cool white bulbs emits light that are really white.
The color of light is measured in Kelvins, 1000 Kelvin represents candle light while 5000 Kelvin is noon daylight. Light globes called soft white or warm white have a color temperature of 2700 Kelvins and emit a pale yellow light, cool white is 4000K which gives that bright white light while daylight at 5000 K gives a bright white light with a bluish tinge. Yellow light like high pressure sodium globes used as fog lights in street lamps have a color temperature of 2100 K.
That would have to be a question for the manufacturers to answer. Most incandescent bulbs emit a yellowish light. The soft white has less lumens than a standard frosted bulb. I believe the reason that they haven't called it a yellow light is because of the obvious reason that they already have a yellow/bug light. Plus, it'd confuse the consumer even more than necessary.
its considered soft as in not harsh or not as bright so instead of harsh white light is a bit of a softer yellow to it or a cream color where as cool light usually has a blue tint to it as to make it cooler...
