[HyperPete]

I think the boot contributes to the color. Still, at at couple of bucks or so for filters, it can't hurt to replace them regularly.

 

[HyperPete]

Anyone can tell me when we need to change fuel filters, mean after how many miles??

There is no schedule. If you experience loss of power under hard acceleration then it might be your fuel filter.
If you have no problems, relax, and enjoy the ride!