Lego Writing systems 6004 Pen in Blue & Yellow. The Lego writing system is the first of its kind. The only pen you connect and build. Mix and match the colorful beads elements to create fun, new designs every time you write. The 6004 pen includes: a create your own pen, 12 bead elements, and a sturdy case for storage and travel. The pen has a soft grip and uses a replaceable ink cartridge. The grip on the pen is blue. The pen has blue ink. Just turn the ring to write. The bead elements are round and square. The bead elements are interchangeable with bead elements from other Lego pens.