title: Coloured Noise in XMDS
body: <p>I'm trying to model non-white noise in XMDS, but not sure how to which type of noise vector to use, or how to encode the memory function of the noise. 
  I'm trying to put in a noise <code>xi(t)</code>, where <code>&lt;xi(t)&gt;=0</code> and <code>&lt;xi(t)xi(t+tau)&gt;=a*exp[|tau|/tn]</code>, where <code>tn</code> is the correlation time of the noise and <code>a</code> is its strength. It seems to me that all the noise types available assume white noise. 
  Any ideas?</p>