A federal judge tentatively approved the Government Printing Office's $2.4-million offer to settle back-pay claims for 350 black printers who won a 14-year-old racial discrimination suit. U.S. District Judge Barrington D. Parker approved the proposed settlement in the class-action suit and scheduled a July 1 hearing to give members of the covered group an opportunity to air any objections. The proposed settlement stems from a 1973 lawsuit brought by black employees of the GPO's offset printing section. They claimed that they were victims of discrimination in promotions to higher-paying and supervisory jobs. When the lawsuit was filed, blacks constituted 90% of the 500-member work force but none was a supervisor, according to attorneys in the case.