Why Use a Blue Lead mechanical pencil?

Sometime, I copied my pencil drawing with copied machine, then stick it under the Manga-paper, and do inking on a light table. Sometime, I used Blue Pencil, and directly draw the pencil drawing on Manga-paper, and ink it directly on same paper.

Why Use a Blue Pencil(Blue Lead with mechanical pencil)?

It's easy to erase, and light colour. Blue lead is easier to clover by black ink.
When inking with black ink, blue lead is easier to identify then black lead.
So it's easier to identify what parts are un-ink.

There are many different brands for the Blue Leads.
(Eg: Staedtler mars micro color, Pentel, Pilot, Uni Color, Faber-Castell TK-Color.)
Make sure it's erasable under

I'm using "Uni Color Blue Lead - 0.5 mm and 0.7 mm", and "Pentel Blue Lead - 0.5 mm".

I used to draw with Cyan(=Soft Blue) Lead, but it's too light, and too blurry for my eyesight. So now I draw with blue lead. I keep trying many tools/ways to fit me needs, So my drawing style/skill keep changing and updated every year.

I encourage everyone, to actually try some different brands of blue leads, and find your best-fit tools to fit your needs.