## 3 Results  
### The Polychromy Scheme  
The stele and the sphinx finial retain noticeable traces of the ancient polychromy, although the distribution and appearance of pigments have been affected by centuries of interaction with the atmosphere and the burial environment, as well as by its post-excavation history, especially on the front of the sculpture. On the shaft, red pigmentation is clearly visible in the background, on the youth's hair, and on the inscription carved on the rectangular base. Conversely, the front of the capital retains little visible pigment, except for a thin red line along the abacus edges and traces of red between the upper solutes. The detailed original painted decoration can only be seen on its front side by means of the PS-enhanced UVL, and, partially, by raking light imaging (Figure 2). Raking light images highlight the incised lines that were likely used to lay out the ornament on the capital (Figure 2B). The sphinx is the section with the most abundant preserved polychromy, particularly on the front. [PERSON], blue, and black pigment remains, in different states of preservation, are visible in several areas of the marble surface, notably its chest, wing (Figure 3A), hair,  
Figure 2: Images of the capital showing the intricate original decoration: (**A**) PS-enhanced UVL; (**B**) raking light. crown, and eyes. The most striking MBI finding on the sphinx appeared in the VIL image (Figure 3B). Bands of luminescence, characteristic of the pigment Egyptian blue, were visible on the wing. Initially thought to be in the areas of the blue pigment visible with the naked eye, the stacking of VIL and VIS images (Supplementary Materials: Figure S3) clearly showed that the luminescence occurred between the visible blue areas, in the sections previously thought to be unpainted. The UVL images of the sphinx highlighted areas that were consolidated as part of past treatments (Supplementary Materials: Figure S2), while, as noted above, UVL of the capital provided details of the highly decorated front (Figure 2A). Remains of blue color were documented by digital microscopy, whose high resolution and high magnification allowed the imaging of pigment remains, even when present as few discrete particles and in recessed areas (Supplementary Materials: Figure S4) such as the crown and the lines that separate the breast feathers from the leonine body. The identification of pigments and the mapping of their distribution were obtained by combining imaging techniques with scientific analyses. Results of multiband imaging and digital microscopy guided the first XRF analysis campaign that was performed in situ on areas with visible traces of pigments and where VIL indicated the presence of vestiges of Egyptian blue. Analyzed areas include: the shaft's background, the youth's hair and arbyballos, the sphinx's wing, chest, head and hair, diadem, legs, and tail end, as well as the capital. Overall, XRF point measurements were characterized by the presence of dominant X-ray lines of calcium (Ca) and strontium (Sr) from the marble, and by lines of sulfur (S), titanium (Ti), manganese (Mn), iron (Fe), and lead (Pb), of variable intensity. In some areas, strong characteristic X-ray lines of copper (Cu) and mercury (Hg) were also detected, indicating the presence of Cu-based and Hg-based pigments. In particular, Cu was detected in the wing, diadem, chest, and tail end, in areas where remains of blue pigment were still discernible. In the wing, the detection of Cu in sections that were luminescent in VIL images confirmed the presence of Egyptian blue. The second, undetermined blue pigment, already observed in MBI in the feathers, showed very intense signals of copper, the significant presence of which suggests another Cu-based blue pigment, likely azurite. The representative XRF spectra of dark red to black areas on the wing feathers and chest showed prominent X-ray lines of Hg, alongside intense X-ray lines of S, indicating the presence of cinnabar (HgS).