Cool is, when you don't take any grub from authorities, like Ms. Li and her School-Colour day.
So, my theory is: Anyone who didn't wore blue and yellow in the episode 305 (like Daria and Jane) are truely cool...
But thinking of it:
The fashion club didn't wore school coulours too. Frightening, isnt' it.
(PS: Kevin and Brittany didn't wore school coulours because they were misinformed.)