In section 6.1 we have shown that the optical continua of our Seyfert galaxies are rich in H and He I absorption lines that cannot be explained by an old stellar population typical of the central region of normal early type galaxies. This is a strong evidence that the optical continua of these Seyfert 2 nuclei cannot be fit by only the sum of the old bulge stellar population plus a power law due to the AGN. Now, we check that the continuum colors are compatible with a young stellar population if we subtract the contribution of the old bulge population of stars. To subtract the old stellar component from the spectra of these Seyferts, we use the equivalent width of the MgI+MgH and the G band features. Comparing the equivalent width of these signatures to the spectrum of NGC 4339, we find that the old component contributes 30% of the light at 4700 Å in NGC 7130 and NGC 5135, and 60% in IC 3639. We have subtracted the old component from the spectra after correcting these with the reddening derived from the UV continuum slope, and then we have computed the U, B and V magnitudes excluding the contribution from the emission lines. The colors derived are U-B=-0.88, -0.91, and -0.85, and B-V=0.19, -0.01 and -0.14 for NGC 7130, NGC 5135 and IC 3639, respectively. These colors are compatible with an instantaneous burst with age between 4 and 8 Myr (see figures 13 and 15 in Leitherer & Heckman 1995). Because the colors depend of the reddening correction aplied to the continuum, we have made an approximate estimation of the uncertainties associated to the colors correcting the spectra by a color excess equal to 0.3 instead of the values listed in Table 4. It is the largest value that we have estimated for the reddening comparing the observed UV continuum slope with the synthesized continuum. In this case, the colors derived are U-B=-0.93, -1.04, and -0.91, and B-V=0.11, -0.1, and -0.24 for NGC 7130, NGC 5135 and IC 3639, respectively. These colors are also compatible with an instantaneous burst with age between 3 and 8 Myr. However, the uncertainty in the determination of these colors is probably large because we have assumed that the old stellar population is affected by the same amount of extinction that the young stars.