Well, at least I can explain the "don't use pure black" part:
Fully black materials simply don't exist in real life. The darkest material ever developed still reflects a tiny portion of light:
http://blog.makezine.com/archive/2008/0 ... 6B48984890
Most "black" materials actually reflect a lot more, so Fletch is right in recommending those values.
If you set something to be RGB 0,0,0, or "pure" black, it will render completely black unless it has another color applied to the specular slot ("reflection"). Why? because n*0=0.
As for the "do not use fully saturated colors" part, I guess it's because most objects use pigments -which are a subtractive method- to produce colors. So you see, pigments actually don't
have any color; they just
reflect certain wavelengths of the light that reaches them, and absorb others. That's why a dark shirt makes you feel hot in a sunny day; it's absorbing a lot of light and converting it to heat. And this "subtractive method" never, ever, manages to produce colors as fully saturated as those produced by the "additive" method of mixing beams of light instead of pigments. Check this Wikipedia article and notice the difference in results between RGB (additive) and CMYK (substractive):
http://en.wikipedia.org/wiki/Color_space
The only objects capable of appearing to have more-or-less fully saturated colors are the ones that do not use pigments, but other methods, such as
interference
http://en.wikipedia.org/wiki/Iridescence
If you own a DLP TV/projector, the color wheel you hear whirring has dichroic filters to split light into RGB before modulating it with tiny mirrors and then projecting it to the screen. But even this method won't produce colors as pure as the future laser-based DLP units, because the lamp inside current projectors produces a lot of wavelengths (read: pure colors) instead of a single one, so if the color wheel was made to filter out all except pure R, G and B you would end up with a very dark image. Thus, these color wheels actually let a mixture of wavelengths go through.
So, the bottom line is:
Unless your furniture happen to be made of laser beams and optic fiber, avoid fully saturated colors. And if indeed you have furniture made of laser beams and optic fiber, please post them to eBay, you'll make a lot of money.
Unless your walls happen to use a material darker than what is currently possible, don't use 0,0,0 black.
I can't explain the "don't use pure white" part, but I'm sure someone will chime in and clarify that.
I'm no expert, though, just as curious as you are.
