usually the main cast stands out based on their hair color, which is typically their palette's primary one
satoko is purple, marin is blue, kuro is kuroi, it's reinforced when wearing their quasi-uniforms as seen in the op pic, roboko is also purp as a copy of satoko
and you can see in
>>7379 other ninjas' designs feature a main color as well that 3/4 times is the primary one, alongside a secondary complement
the one that really doesn't care about standing out or having a recognizable design is konoha, which fits her character
>>7377they're all outlandish killers