colour code 
noun
A system of marking things with different colours as a means of identification.She uses a colour code to help tell apart her 22-month-old identical triplet sons....
- The website will be updated weekly using a colour code to denote changes, with gold heralding the peak period.
- To mark the six months since the September 11 atrocities, your administration has launched a national colour code showing the level of the terrorist threat facing the country.
verb
(colour-code) [with object] Mark (things) with different colours as a means of identification: each unit is colour-coded for clarity...
- The parents of a 22-year-old woman who was killed by a drug mix-up said she had died for the sake of a few pence - the cost of colour-coding the different dosages.
- Thoughtfully, the boxes for the different parties are colour-coded according to party.
- The different virus families are colour-coded.