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[Abridged] We study the spectral properties of intermediate mass galaxies asa function of colour and morphology. We use Galaxy Zoo to define threemorphological classes of galaxies, namely early-types (ellipticals), late-type(disk-dominated) face-on spirals and early-type (bulge-dominated) face-onspirals. We classify these galaxies as blue or red according to their SDSS g-rcolour and use the spectral fitting code VESPA to calculate time-resolvedstar-formation histories, metallicity and total starlight dust extinction fromtheir SDSS fibre spectra. We find that red late-type spirals show lessstar-formation in the last 500 Myr than blue late-type spirals by up to afactor of three, but share similar star-formation histories at earlier times.This decline in recent star-formation explains their redder colour: theirchemical and dust content are the same. We postulate that red late-type spiralsare recent descendants of blue late-type spirals, with their star-formationcurtailed in the last 500 Myrs. The red late-type spirals are however stillforming stars approximately 17 times faster than red ellipticals over the sameperiod. Red early-type spirals lie between red late-type spirals and redellipticals in terms of recent-to-intermediate star-formation and dust content.Therefore, it is plausible that these galaxies represent an evolutionary linkbetween these two populations. They are more likely to evolve directly into redellipticals than red late-type spirals. Blue ellipticals show similarstar-formation histories as blue spirals (regardless of type), except they haveformed less stars in the last 100 Myrs. However, blue ellipticals havedifferent dust content, which peaks at lower extinction values than all spiralgalaxies.

The different star-formation histories of blue and red spiral and elliptical galaxies