My favourite colouring medium is ProMarkers but it always annoyed me when I had to hunt around for the colours that I wanted! I saw this idea in a magazine and decided to give it a try! It's fab, easy to use but sadly not too portable!!
It's basically a DVD storage box from Ikea and DVD boxes without covers. In Microsoft Word I created boxes which I then named with the colours and a space to colour it in. I put the colours into order using one of the colour charts you get with the packets of ProMarkers - this makes it really easy to work out which ones to blend together! I then put the little tables along the spine of the DVD box. I put a coloured adhesive dot at the end of each pen to make it really easy to find the colour needed.