code: def get_colors(catalog):
      
      print("Get Colors")
      a = pyfits.open(catalog)
      data = a[1].data
      a.close()
      all_ids = data['LAMOST_ID_1']
      all_ids = np.array([val.strip() for val in all_ids])
      # G magnitude
      gmag = data['gpmag']
      gmag_err = data['e_gpmag']
      # R magnitude
      rmag = data['rpmag']
      rmag_err = data['e_rpmag']
      # I magnitude
      imag = data['ipmag']
      imag_err = data['e_ipmag']
      # W1
      W1 = data['W1mag']
      W1_err = data['e_W1mag']
      # W1
      W2 = data['W2mag']
      W2_err = data['e_W2mag']
      # J magnitude
      Jmag = data['Jmag']
      Jmag_err = data['e_Jmag']
      # H magnitude
      Hmag = data['Hmag']
      Hmag_err = data['e_Hmag']
      # K magnitude
      Kmag = data['Kmag']
      Kmag_err = data['e_Kmag']
      # Stack
      mag = np.vstack((
          gmag, rmag, imag, Jmag, Hmag, Kmag, W2, W1)) # 8, nobj
      mag_err = np.vstack((
          gmag_err, rmag_err, imag_err, Jmag_err, 
          Hmag_err, Kmag_err, W2_err, W1_err))
      # Make g-r, r-i, i-J, etc
      col = mag[:-1] - mag[1:]
      col_ivar = 1/(mag_err[:-1]**2 + mag_err[1:]**2)
  
      # There's something wrong with the i-band, I think..so the second color r-i
      #bad = col[:,1] < 0.0
      #col_ivar[bad] = 0.0
  
      return all_ids, col, col_ivar
docs: Pull colors from catalog
  
      Parameters
      ----------
      catalog: filename