Does clipping noise colour the spectrum
Clipping is a non-linear operation and it introduces new frequencies, so it will change the spectrum's shape. The text you quoted is pretty clear on that.

Just as a quick demo, I generated flat noise in Matlab, limited in frequency to the 100 to 300 Hz range. The spectrum is: 

Note that the spectrum is close to zero outside the specified range. Also, this noise is not white; it is flat (or would be if I could simulation an infinite number of samples). White noise, by definition, covers the entire frequency range.

I clipped all amplitudes larger than 0.75 to 0.75, and the resulting spectrum is:  

I think the difference is clear.