When I created my characters I really took time in choosing everything carefully, from face/eye/nose shape to hair type and color.
When I draw them individually and really take my time in the drawing you can actually see the difference. Even with two of my characters that are twins, I made them fraternal twins because I didn't want them to be identical.
But my comic being b/w even for me I find that there is a point when I start making the same faces, specially when drawing the eyes, sometimes I go back and redo everything, others times Im just too lazy and drawing the hair really helps differentiate from them.
I'm not really sure if I've been making this mistake tbh... 😰
I do know that dissent females have this problem, they all look the same... and I've heard that Bleach, in the manga, ended up with this problem...not sure....