The Colour Index shows the change of
the two main shades throughout the
whole Picture Book Edition. Each double line corresponds to
a single book of the edition (from A to Z).
Every line consists of 150 ribbons showing the
colour value of the first square on every
page (placed in the upper left matrix corner)
for main shade 1 (upper stripe) and main shade 2
The figure illustrates the colour evolution over the 26 books of the
Picture Book Edition running along 390.000.000 digits of Ludolph's Number.