Making Colour-rings and FlagsColour-rings and Flags must be made of a plastic that is U.V. stable, colourfast and also strong enough to cope with a range of environmental conditions; such as being rubbed against rocks or submerged in mud or salt water. Colour-rings can either be overlap-ring or split-ring in design. Both of these ring types look alike to the observer but differ slightly in how they are fitted. See making Colour-rings. Flags look similar to rings but have an extra 'tag' that protrudes a short way out to one side. See making Flags.
A range of standard colours are used and biologists planning to use Colour-marks must register with the Colour-marking Register.