For some reason, lawyers have traditionally used paper that that is 8.5 by 14 inches long instead of the 8.5 by 11 that is standard in all other kinds of offices. I think the courts used to insist that any briefs filed with them had to be on paper of that size (white of course), besides meeting other arcane and inscrutable rules. I think the rule has been abolished, at least in Minnesota courts, but lawyers are very tradition-bound. One lawyer I am acquainted with insists that his secretary not use any abbreviations in his correspondence. It must be "Saint Paul, Minnesota" not "St Paul, MN".

So legal pads, for note-taking, were ORIGINALLY and TRADITIONALLY strictly yellow paper with horizontal blue lines and a red vertical line to mark the left margin, bound with staples at the top, and perforated so that when you tore off a sheet it would be exactly 8.5 by 14 inches. But today, monster office-supply stores sell "legal pads" in white or any pastel color you fancy, and at least 3 sizes. The only consistent characteristics are the binding, perforation, lines (in whatever color), and the fact that they fit into a hard vinyl-covered folder which is sold separately.