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The traditional use of fixed apertures in determining the well knowncolor-magnitude (CM) relation of early type galaxies, coupled with the presenceof radial color gradients within these systems, introduces a bias in the CMrelation itself. The effect of this bias is studied here deriving a CM relationwhich is based on color measurements carried out homogeneously within anaperture of radius equal to that of the galaxy effective radius. A sample of 48giant early-type galaxies in the Coma cluster, with CCD observations in the U-and V-band, is used for this derivation. It is found that internal radial colorgradients in early-type galaxies cannot be neglected when discussing the colorsof these systems, and that the CM relation derived using color measurementswithin the effective radius is significantly flatter than those based onfixed-aperture color measurements. With the presently available data it isimpossible to determine whether the relation is completely flat, or whether asmall correlation is still present between galaxy color and luminosity.Comment: 18 pages, with 5 figures; to appear in the May 2001 issue of A

Internal Color Gradients and the Color-Magnitude Relation of Early-Type Galaxies