The concept of coloured coins/using the blockchain to notarize documents is a game-changer because it does not rely on a centralized authority to maintain. It is a publicly available ledger where no third party need be trusted. With bitcoin we can be our own bank.
What do you mean by coloured coins? Many coins are fully centralised, they are pretending to be decentralised and they are not, even Ethereum can't deny this today, at first it claimed to be decentralised and later it turned to full proof of stake coin, there are too many examples like this with alternative coins.
Bitcoin that's fully decentralised is affected by ETF and institutions around the world, the centralised authority and power have laid their hands on Bitcoin and today it feels more centralised, even the users who we should trusted are all using Bitcoin like it's centralised, everyone is the reason why decentralised side of Bitcoin isn't working well.