  We have done a robust statistical study of the behaviour of color profiles
for 257 Sbc galaxies, having determined (B-V) and (U-B) color gradients, as
well as color indices of bulges and disks separately. Applying a bidimensional
decomposition technique to model the brightness profiles of bulges and disks,
we obtained characteristic structural parameters for 39 galaxies. Among the
main results obtained, we point out: 65% of the galaxies have negative color
gradients (reddish inward), 25% have no gradients, and 10% show positive
gradients; galaxies that show no color gradients tend to be barred; we confirm
the correlation between the color indices of bulges and disks; the absence of
correlation between color and metallicity gradients suggests that the excess of
barred galaxies with zero or positive color gradients reflects a difference in
the behaviour of the mean age of the stellar population along barred and
unbarred galaxies; galaxies with zero or positive color gradients show a slight
tendency of having larger bulges, with a greater central concentration of
light, and we confirm the correlation between the scale lengths of bulges and
disks. These results are compatible and favourable to the secular evolutionary
scenario, in which stellar bars induce radial mass fluxes to the central
regions of galaxies. (Abridged)
