A 100W incandescent has a color temperature of about 3000 K, while the sun is 5700 K, so yes, it does appear more yellow. Because both incandescents and the sun

A 100W incandescent has a color temperature of about 3000 K, while the sun is 5700 K, so yes, it does appear more yellow. Because both incandescents and the sun are essentially black bodies, their color temperature is their actual temperature (the filament in an incandescent is about 3000 K). Other light sources, such as white LEDs can produce 5700 K light, but their spectrum is actually much different from solar. They can get away with emulating 5700 K with only two or three wavelengths, while a black body emits approximately continuously throughout the wavelengths (this is due to the way correlated colour temperature is calculated; incandescents and the sun waste a lot of energy on non-visible infrared wavelenghts). For electricity efficiency purposes, LEDs are great, because they don't waste electricity generating wavelengths we don't see (or ones that are cancelled out by other wavelengths). But for SAD, white light is likely not the requirement; our eyes have cells that have different sensory response based on wavelength -- apparent colour is an afterthought. Some of these cells are thought to affect SAD through melatonin inhibition, so the big question would be: what wavelengths are these cells most sensitive too, so we can optimize lights for them? Some cursory googling says that the jury is still out on that one. tl;dr: colour temperature of light isn't what we should be optimizing for when dealing with SAD, because our eyes have spectrum sensors, not colour sensors. Be wary of marketing hype because you can likely get away with $1 lightbulbs, instead of $300 lamps.