Colour coding is a very powerful tool, and I personally use it wherever possible. As a standard practice (atleast in India) the documents for accounts and stores, have specific coloured copies for customer and individual departments. Similarly, for purchase orders there are four different colours on respective copies. I have adopted the colur coding on documentation for production and quality as well. Going a step ahead, I issue different colur markers to inspectors who sign & put a mark on the components checked by them. This helps in tracing back a non conformity!
Furthermore, I have alloted colour coding for each customer, and these colours are painted on the dies and I am further putting these colour codes on the drawings as well. I am also using Green, Yellow & Red tags for Okay, Rework & Rejection respectively (which I feel is a universal practice)
Overall I feel that colour coding is a very effective tool, used since time immemorial.
Umang