A mobile phone accessory for a smartphone, including a support and handling casing with an internal space, an inner face, an orifice for association with an AOI target, located within a light incident spot, and a rear wall portion, a lighting element, to illuminate the spot, a camera field of view, to make a reflection photo of the spot, a scattering plate, having a scattering opening with a center and a center, including high-opacity and low-opacity portions, which include color measurement targets, fixed on the face of the front wall portion, sidely with the measurement orifice, through the scattering opening is seen the spot, the scattering plate has from a high-opacity degree on and around the center to a low-opacity degree at the opposite and near the scattering opening, the scattering plate making homogeneous the lighting and the extension of the AOI target and color measurement targets.