Gabriel Lippmann — Scientist born on August 16, 1845, died on July 13, 1921

Jonas Ferdinand Gabriel Lippmann was a Franco-Luxembourgish physicist and inventor, and Nobel laureate in physics for his method of reproducing colours photographically based on the phenomenon of interference... (wikipedia)

Life is short and progress is slow.
In the case of composite colour, an infinity of systems must be obtained for maxima infinitely slight and with an infinity of interval values separating them - that is to say, the whole thickness of the sensitive layer is occupied in continuous manner by these maxima.
Most of these pictures, taken while travelling, were developed on the mantelpiece of a hotel room, which proves that the method is easy enough to carry out.
The problem of direct colour photography has been facing us since the turn of the last century.
When the shot is afterwards subjected to white light, colour appears because of selective reflection.