It is very impolite to do that. Surely you don't like someone to shout at you. Do not spam. If you are caught doing that, you will be banned from using the chat server. Avoid using excessive colours Using colours is not going to get you any special attention.
Some users dislike the use of colours because colours make the channel messy and disorganized.
Be polite and friendly to everyone. If you are polite to others, they will do the same to you. Let's work together to build a friendly chat environment. Do not ask for ops or access in any channel. It is consider as begging for power and you will usually get ban from the channel if you do that.