Fig. 5

Summary of red–orange color analysis. a Representative image of red–orange color field, from Renshi (32.71). b XRF spectra of red–orange areas. The Pb M-line at 2.6 keV overlaps the S K-line, but given the abundance of the L-lines here the peak can be assigned to Pb. c Regular Raman spectra of a reference red lead standard compared to spectra collected from red–orange areas. d SERS data and GA fitting results for red–orange areas from (i) red post on Ono no Komachi (32.75), (ii, iii) two areas of the red decking on Renshi (32.71), and (iv) red railings on Koshikibu no Naishi (32.69). Blue traces are the sample spectra, black traces are the fit spectra, and red traces are the squared difference. The inset plots to the right show the correlation between the sample and its fit spectrum