one f ma teacher once told us dat it means royal blue color n it is prticularly to disallow d sky blue ink n blank n other colors ink.... but i dnt think its evr takn dat seriously fr shades in blue, by checker.. jst make sure dat u r using only blue ink.. i believ...
BLUE BLACK is a shade of Ink Available with Parker and Chelpark, it is a mixture of blue and black. Put simply it is a blackish blue Hue ink used for Inkpens!
( i know this question was asked many days ago, but i saw it today, and i used to write with blueblack ink, dats why i thought i'll answer this).