Fig. 7: Raman spectra of blue pigments acquired from different areas.

a Raman spectrum acquired from points of C2, C7, C10, D1, D11, F6; (b) Raman spectrum acquired from point of E6; (c) Raman spectrum acquired from points of B1, B8, E2, E5, F2, G3; (d) Raman spectrum acquired from points of G2.