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In this Letter, we analyse the radial UV-optical color distributions in asample of low redshift green valley (GV) galaxies, with the Galaxy EvolutionExplorer (GALEX)+Sloan Digital Sky Survey (SDSS) images, to investigate how theresidual recent star formation distribute in these galaxies. We find that thedust-corrected $u-r$ colors of early-type galaxies (ETGs) are flat out to$R_{90}$, while the colors turn blue monotonously when $r>0.5R_{50}$ forlate-type galaxies (LTGs). More than a half of the ETGs are blue-cored and haveremarkable positive NUV$-r$ color gradients, suggesting that their starformation are centrally concentrated; the rest have flat color distributionsout to $R_{90}$. The centrally concentrated star formation activity in a largeportion of ETGs is confirmed by the SDSS spectroscopy, showing that $\sim$50 %ETGs have EW(H$\rm \alpha$)$>6.0$ \AA. For the LTGs, 95% of them show uniformradial color profiles, which can be interpreted as a red bulge plus an extendedblue disk. The links between the two kinds of ETGs, e.g., those objects havingremarkable "blue-cored" and those having flat color gradients, are less knownand require future investigations. It is suggested that the LTGs follow ageneral picture that quenching first occur in the core regions, and thenfinally extend to the rest of the galaxy. Our results can be re-examined andhave important implications for the IFU surveys, such as MaNGA and SAMI.

Quenching depends on morphologies: implications from the ultraviolet-optical radial color distributions in Green Valley Galaxies