Red to Orange in c. 1910 T and E cards.

[G1911]

Originally Posted by steve B

Red pigments and dyes have been troublesome almost as long as we've had them.

Prior to the bright red of cochineal dyes from Mexico, the primary one in Europe was Alizarin Crimson. Which created a range of red to brown colors depending on the additives used. The most popular shade? Turkey Red.... Yes, a specific red developed in the middle east.

It was eventually discovered to be made from two different colorants in the same plant root, Alizarin and purpurin, the latter of which fades easily. Not that Alizarin doesn't also fade somewhat easily.
This became the first chemically synthsized dye in 1868 or so.

The reds from Cochineal (Insects) are durable, cloth dyed nearly 2000 years ago that has survived away from light is still red.
But as far back as it has been used artists have known that it will fade with light exposure, often turning towards brown before fading away altogether. (But not water and soaps, hence it's wide use in cloth and cosmetics. )

I'm not sure there's a lightfast red available today.

I knew you could give us the "why" it's the red that does this with time. Thank you