Who made these rules?

I do know that black is the most used color ink as it derives from the old fountain ink pens. It is customary to use black as if the document is copied and or fax it maintains its original signing and will not fade during the transaction.. Where as if blue was used and it is later then copied and or faxed the color gets distorted.

The....GOVERNMENT! ha just kidding on a serious note I have no idea i guess it just follows tradition and maybe originally came from the school/educational system.

That is a very good discussion, KRTWORLDWIDE, but unfortunately, I do not have the answers, I am hoping somebody will be able to throw more light on this discussion.

I have no idea. I guess blue/black are neutral yet professional colors. Red stands out and it's typically the color for "WRONG." But I've never heard of the green signatures thing. I actually used to have a teacher who would correct things in purple because he felt it was a calmer color than red. When students see read all over a test they automatically feel like they did poorly.