Left panel: colour–colour diagram with the ACS and WFC3/IR magnitudes. Gray crosses mark the full sample of common sources, black circles show selected GC candidates (see text). Right panel: comparison between WFC3/IR photometry and the IRAC2 data from Goudfrooij et al. (2001a). In both panels the predictions from SPoT simple stellar population models with different metallicity are shown with different colour/line styles ([Fe/H] = −2.3, −1.4, −0.7, −0.4, 0.0 and +0.4 dex shown with dark-yellow, cyan, magenta, green, blue and brown, respectively). The age range is 3 to 14 Gyr. (See electronic version of the Journal for a colour version of the figure.)