what is the use of coloured pokemons?

is there any special about it?

It increases your fame and may make you look cool and as time passes its value increases and its worth keeping it

They're different and worth more than normal Pokemon.
For example.
A normal Shinx rates around a coins, while a Luminous one rates 16k.
And like Shadow adi said, its rate increases over time as well. People collect them because they're something different, and they look cool, and are worth something.

Thankx shinxey for supporting my opinion mptmpt2 now did u get the need for coloured poke in team but one more as it becomes unbase its rate changes beware of that

It doesn't change too drastically if it becomes unbase (not level 5), but it DOES lower the rate, and make it harder to sell.trade, as people are mainly LF base Pokemon.

i agree with shixey and adi on this one. how ever some colored poke like shiny and ancient have more hp

I always thought all colored pokemon and regular pokemon were similar in stats, but the only thing different was the fact that their colors are different. Are all the "coloreds" different in stats like the shiny and ancient ones?