With "For Colored Girls Who Have Considered Suicide/When the Rainbow Is Enuf" set to follow the current "Bubbling Brown Sugar," the National has two more new black productions on the horizan.

"Timbuktu" inspired by the musical "Kismet," has a setting in Mali and will boost Melba Moore, William Marshall, Eartha Kitt and Gilbert Price heading the cast, which director-designer Goeffrey Holder very much in evidence.He was here this week measuring the E Street stage.

Several new songs will be added to the Robert Wright-George Forrest score, which introduced "Stranger in Paradise" and "Baubles, Bangles and Beads." This will be at the National in November, replacing "Spotlight," postponed because of a bone-break suffered by star Dan Dailey.

December will bring James Earl Jones as "Paul Robeson," a neww mono-drama by Philip Hayes Dean to be staged by Charles Nelson Reilly.

ASTA has found a new home on Capitol Hill. Settled in 12th Street for four seasons, the acting group now will have two performing spaces at 507 8th St. SE, the larger seating 140, the smaller 80 (20 more than it had downtown), Director Dona Cooper's eason will begin with "Merton of the Movies," the comedy hit of this era by George S. Kaufman and Marc Connelly, playing from Oct. 26 through Nov. 20. Starting Nov. 30 will come a solo drama, "Bernhardt," by Sarah Ban Breathnach. "Private Lives" will play Jan 11, Feb. 12, "Playboy of the Western World" March 8-April 9 and "La Ronde" May 3-June 4. Subscriotion details at 543-7676.

After Mary Martin and Anthony Quayle close Saturday night at Eishenhower in "Do You Turn Somersaults?" the stars will have three-week holiday from their two-character comedy by the U.S.S.R.'s Aleksei Abruzov, then a tour which will take them to Wilmington, Chicago, Fort Lauderdale and Boston before a New York opening in January.

Sam Levene declares that he has not left "The Merchant" company because his role has been cut down, but purely because of his emotional shock over the death of his friend and co-star Zero Mostel. He says: "I was too close to Zero and a play we both loved, to do it without him."

Barbara Cook, Lyn Frizzell Kay Granger and the comedy group Red Shoes Walking will be on the Dialogue for Human Rights benefit Oct. 1 in hte Kennedy Center Concert Hall. WMAL's Tom Gauguer and Gloria Steinman will be the emcee's for the evening sponsored by the Gay Activists Alliance, the Gertrude Stein Democratic Club and local chapters of NOW. Seats at the box office and through Instant Charge, 957-0900.

It's easier than buying theater tickets used to be, and Bob Bialek's three Discount record and book shops intend to make it easier still. Seats for almost all area attractions are now being made available, at all three stores. Also in theis line, most major London theaters have now agreed to charge seats through American Express cards. Time was you had to go to the theater twice, first with the cash for the tickets, then the body for the seats.

Douglas C. Wager, coordinator for Arena Stage's In the Process series, has been named the theater's first time literary manager. "Dramaturg" is the old little for this traditional theater post, revived by Laurence Oliver's appointment of Kenneth Tynan at England's National Theater and dnow adopted by several resident theaters in this country. He met Arena's Zelda Fichandler during her Boston University seminars.

The Washington Area Feminist Theater's year of workshops and short subjects ends with a return to production for an "An uncommon Occurence," an improvisation exploring "the struggle of women reaching in to themselves and out to each other." Performances run from next Thursday, Sept. 29, through Sunday, Oct. 2, at All Souls Church, 16th and Harvard Sreets NW. There will be performances Oct. 6 through 9 at the Earth Onion Women's Theater. Details at 638-0008.