I do agree that blue is better for signatures. But it does seem to have become NOT a standard like it used to be.
I used to use blue exclusively - used to bug me to use a black pen - but now - I don't know when or why - black has become my standard. I am very picky about is what ink I'm using. It irks me to no end to use a pen that will smear or bleed if it gets wet or over the passage of time. So I have stuck to ball-point pens while everyone around me goes to roller balls and what not. Another bugaboo I have is point size - I can't stand writing with fine point. It seems to scratch the paper and it's like nails on a blackboard to me. For me writing needs to be smooth - especially since I press hard --- I'm the one who's paper curves and crinkles when turned over...
DonnaP99