Below is an 8 month lightfastness test of the 36 pencil Anniversary set of the Faber Castell Polychromos. There is also a swatch from a pencil that I bought open stock, nr 225 from the regular line of Polychromos.

The strip to the left in the picture below has been laying in a dark drawer, so that is how they look when you draw with them. The two strips to the left have been exposed to sunlight for 8 months. They have been taped on the inside of a window.

Results:

From the set of 36: All appear lightfast except for four of them: nr 5, nr 32, nr 29, and nr 21.

The open stock pen nr 225 shows a minor color change, and the same goes for nr 35. I’m not sure how visible it is in the scan, but the hue is a tad colder. I’ll put the stripe furthest to the right back in the window, and see how it will look after a few more months.

The picture below shows the swatches before i divided them into strips, vertically.