We are performing a thorough analysis of the internal colour gradients of early-type galaxies (ETGs), examining a sample of about 5,000 nearby massive systems, with optical+NIR data from SDSS+UKIDSS-LAS surveys. The large wavelength baseline (including grizYJHK wavebands) helps us to infer age and metallicity radial gradients of ETGs, minimizing the effect of the age-metallicity "conspiracy". I will discuss how colour, age, and metallicity gradients depend on galaxy properties (e.g. mass), as well as on the environment where ETGs reside (i.e. field, groups, and clusters). These dependencies imply new constrains on our picture of how the most massive galaxies form and evolve.