This undated photo shows a traditional pattern for courtyard doors filled by a netizen with coloured pencils. [Photo: weibo.com]

The Palace Museum in Beijing will issue a series of colouring books to celebrate the 90th anniversary of its establishment this October.

Titled "Color the Forbidden City", the series includes three black-and-white pattern books for people to colour, with themes on traditional architecture, costumes and artifacts, respectively.

The preliminary drafts of the first two books have already been completed.

Unlike Secret Garden — the international best-selling colouring book based on the designer Johanna Basford's creation and imaginations — pictures in this series come from actual decorations and collections inside the Forbidden City.

Experts on the Forbidden City's architecture have been invited to write a brief introduction about each pattern in the book, so readers can learn the cultural and historical significance of the patterns while colouring.

Founded in 1925, the Palace Museum is located inside the Forbidden City, China's imperial palace in service from 1368 to 1912. The accumulated royal treasures are the basic sources of the current collections in the museum.

Last month, the museum initiated a campaign through its official Sina Weibo account, inviting netizens to colour three black and white patterns, which has attracted wide participation.