That’s a lie. Blue scans but it works nicely if you’re going to use black ink over it and scan the drawing in (that’s what I did for Cheese Dreams in the Dreams derby).
PS - I’m not calling you a liar, since you said you heard it. I’m not sure what the purpose of using blue pencil is…for the plane I used a mechanical pencil then went over it with a ballpoint pen.
Some old monochromatic photocopiers couldn’t distinguish between light blue and white paper, so you used to be able to write markup/edit notes on paper with a “non photo blue” pencil and it would disappear on a photocopy. I think modern scanners (which ought to be able to pick up color!) don’t have this limitation (or is it a feature?), but you can still buy the non photo blue pencils.
