Re: How do we see colors?

It is more the former --- "...we see a color of a shirt as red because all of 
the other colors of the specturm are being absorbed and red is being 
reflected".

Actually, if you put the light from the shirt through a spectrum analyser, you 
would find a range of colors coming from the shirt - but with more light (or 
greater intensity) in  the red part of the spectrum.  The red part of the 
spectrum, shown below,  tends to be from 650 to 700 nm wavelengths. 
So, the red shirt may have some light in, say, the orange and yellow part of 
the spectrum (around 580 to 650 nm), but more of  the light would be in 
the 650-700 nm wavelength  raise, so you would sense it as being red.

Here are a couple of images of the spectrum: