An ink for marking pens according to claim 1, which comprises a red dye represented by the formula (III) ##STR47## wherein each of R9 through R14 is independently --H, --CH3 or --C2 H5, R1 is --CH3 or --C2 H5, and R8 is an alkyl group or a substituted alkyl group of C6 -C18, an ethanol-soluble resin, and ethanol.