•New, useful information about the pigments used by artists of the time.•Spectroscopic techniques allow to unequivocally identify the chemical composition of pigments.•The most abundant colour in the paintings was red in various hues.•The techniques used by the artists is mezzo fresco and secco (with organic binders). Fragments of a wall painting from a High Roman Empire building in Córdoba, southern Spain, were examined. The aim was not to extract archaeological information, but rather to precisely identify the materials from which the pigments were obtained and how they were applied. The mortar receiving the pigments was also analysed. Determinations were done by using X-ray fluorescence (XRF), micro-Raman (μ-Raman) and Fourier transform infrared (FT-IR) spectroscopies, X-ray diffraction (XRD) and scanning electron microscopy coupled to energy dispersive X-ray spectroscopy (SEM–EDS). The XRF technique allowed chemical elements to be identified and, in combination with SEM–EDS, their spatial distribution in the fragments to be elucidated. Similarly, μ-Raman spectroscopy and XRD allowed the chemical species in the mortar to be identified. The pigments found were typical of the Roman colour palette used in Hispania and included various types of ochre (yellow and red), mixtures containing green earths, white (calcium carbonate), black (carbon) and precious materials such as cinnabar and Egyptian blue. The mortar was found to have been prepared in the traditional manner from limestone and sand. The pigments were applied in solution or suspended in lime water, a technique that was latter named mezzo fresco. By exception, cinnabar and Egyptian blue were applied with the secco technique and the aid of an organic binder. Some fragments contained several paint layers. In any case, the paint was invariably applied directly on an unprimed wall.