If they didn't have very pure filters with which to test the spectral sensitivity, then they may have confused themselves interpreting the results of testing. Prisms were certainly available to separate colors in the 1850s, but diffraction gratings, while invented in the very late 1700s, did not become somewhat available until ruling engines were successfully built in the very late 1800s.
I'm reminded of the show "Connections". To quote The Human League and their song, "The Black Hit of Space", perhaps we need to
"Get James Burke on the case..."