Simply default color of the tori changes whenever a new player upgrades on a higher belt (blue,green,yellow etc) and it goes till its black belt and then continues from god belt
This would just be kinda user friendly and toris wont look like shit all the time

The whole point of gradients and other color items is exactly that, you unlock certain colours at certain belt milestones. The only difference is that it's not default and you have to buy it, which actually gives you something to work towards. Don't see how your suggestion could bring improvements when around half of all colours in market are affordable for average users

Most of the players dont know how to buy and there are alot of ugly alt accounts daily so changing colors on default toris would just make the game more colorfull and not just orange all the time, the normal blue red etc colors could get removed from torishop to make them default for belts , or they can release new colors a bit less saturated to still make players want to buy better colors. I am tired of these orange ugly toris

When you say ugly do you mean they just like how the Tori already is? I don't think it's okay to force their default Tori to change. I think keeping the defaults is fine. Everyone has their own preference, and if someone wanted to change their tori up they can ask someone to help them learn how to.