A first blue ink for marking pens of the present invention comprises a blue dye represented by the formula ##STR6## (wherein each of R9, R10, R12 and R13 is independently --H, --CH3 or --C2 H5, each of R15 and R16 is independently --H, --CH3, --C2 H5 or a phenyl group, and R8 is an alkyl group or a substituted alkyl group of C6 -C18), an ethanol-soluble resin, and ethanol.