The Chemistry of Perfume Colour Change

We often hear people saying that perfume will change color, and more people will say that it seems to turn darker after a long time? This should be oxidation, right? Is this phenomenon bound to appear, why and how did it appear, and can it be reversed or avoided? The Perfume Material and Science Committee of the Hong Kong Perfumery Association tried to explain it in terms of chemistry. Only those who have completed the Asia Perfume Foundation APF Award in Perfumes Level 2 or equivalent qualification course (Hong Kong Perfume School Perfume Appreciation and Perfumer Craftsmanship (Postgraduate) certificate course) are accepted to enroll