Pseudo color ΔR_M =  −2.5   log (M_w/M), where M is the intrinsic flux ratio derived from our spectra using the MmD and M_w is the flux ratio measured in 3 different wavelength ranges: (1) the region around 7500 Å (blue diamonds), (2) the H-band (red triangles), and (3) wavelengths redder than H-band (black circle). Open symbols are used for the systems where our spectroscopic estimate of M disagrees with the value at wavelengths redder than H-band (see Sect. 4.4). The objects are ordered from left to right as a function of increasing microlensing of the continuum (note that the steps are not linear). The gray labels provide the name of the systems (shortened to the first 4 digits of the RA) and the upper axis indicates the redshift of the source.