legal advice

The main benefit of custom blue-ink pens is that you can quickly discern an original signature from a photocopy. This has made the blue-ink pen the preferred choice among lawyers, title companies and the medical profession across the nation.
Now, nearly every time I speak the words you just read, someone brings up color copiers. "Yeah, but what about color copiers, huh?"
Well, the fact is, you cannot color copy a blue-ink pen signature and fool anyone who knows the secret. And here's the secret: If you look at a blue-ink pen signature with a jeweler's or printer's loop, and you see hints of red and black in addition to the blue, … you're looking at a copy. The other dead giveaway is if you see little dots of color as opposed to solid color with streaks in it. The streaks in an original blue-ink pen signature run with the curve and flow of the stroke. Streaks in a copy will be straight, either horizontal or vertical.
The reason a color copier or scanner/printer can't accurately reproduce a custom blue-ink pen signature is because color copiers and scanner/printers use CYMK (Cyan, Magenta, Yellow and Black) to make colors. The copy of the blue-ink pen signature must use dots of cyan, red and black to reproduce the color of the blue-ink pen. If the copier or scanner/printer uses RGB (Red, Green & Blue) you'll likely see dots of green and red.
Understanding how color copiers and printers work is important because it will give you the power to detect if someone has altered what is presented as a copy of an original.
Upon close examination, if you see a combination of what looks to be an original signature and the tell-tale signs of a copy — then you know that the copy was altered. This is important if you're trying to figure out if someone is lying. For instance, if someone tells you the document before you is an exact copy of the original, then all parts of the signature would contain dots and bits of color. But if you see a combination of solid color and dots, you'll know the copy has been altered.
In addition to delivering the ability to quickly tell an original signature from a copy, another benefit of blue-ink pens is largely cosmetic — it simply looks good.
Often a blue-ink pen signature looks striking on the page set off against a sea of black type. In addition, if you use a Post Script (PS) at the bottom of your letter, signing the letter with a blue-ink pen can drawn attention to the bottom of your page immediately.
If you feel that only a black-ink signature is appropriate for a business letter, you can still use blue ink to hand write a PS or to make other attention getting notations to the letter.
If document security issues are important to you, you may want to invest in a jeweler's or printer's loop — the equivalent of a pocket microscope. They are available from most graphic supply stores and where magnifiers are sold. Keep in mind, a regular magnifying glass won't give you the magnification you need to see the detail. So ask for a loop.