Masking tape

This stuff is amazing, it totally appeals to our love of things that are a clever take on a simple product. Made from Washi paper they can be layered up, written on and torn. Available in a selection of very doubleyou colours.

This great UK based website sells direct:
http://www.presentandcorrect.com/item.php?item_id=461

And this website specialises in coloured Japanese 'Happy Tape'. So there is plenty to choose from.
http://babyology.com.au/miscellaneous/happytape-for-happy-occasions-2.html

The masking tape is also available at the Gallery Store, GoMA