Its rather the other way round. The "colouredness" of a bitcoin amount needs to be kept intact actively, by using it only in colour aware transactions. Recall that a "Bitcoin" as such doesn't exist. What you can spend is always the output from a previous transaction you received. Once you mix a coloured output with any other ordinary output, e.g. by using it in an "vanilla" bitcoin transaction, you have lost the colour; what remains is the ordinary value of that bitcoin amount.

Thus, what's required is to create any kind of setup, scheme, protocol, contract or whatever which associates something special to that colour. It boils down to being able to create a limited amount of a specially marked "kind" of coin and to transact in those without central registration.

Of course the hope is that all the commonly used clients will support colour aware transactions out-of-the-box eventually. But for that to happen we need cunning ideas to make people "want" to do such colour aware transactions.