There was another birthday party this weekend. There were fewer guests than at the one for President Reagan, but there were lots of gifts, including a turtleneck pullover with the logo "Forste Damfrisor" -- that's "First Hairdresser" in Swedish. And a cake with marzipan likenesses of Julius (he wants everyone to forget his last name) and his client, the first lady.

Julius was late getting to his birthday dinner at Germaine's Saturday night. There was Mrs. Reagan's hair to do at the White House and then more work with the sable set at the Madison Hotel. His schedule wasn't as rushed as the night before, though, when he had five appointments scheduled for the hour and a half just prior to the White House birthday surprise for the president.

(Impatient for the elevator to take him from the 15th to the 14th floor at the Madison Friday night, Julius said that he dashed into the fire exit only to find he was locked into the stairwell. After pounding on the door for 15 minutes, actress Irene Dunne, who had been pacing the floor waiting for him, finally rescued him, he added.)

Julius' Washington business associate, hair stylist Robin Weir, hosted the small dinner. Four years ago, Weir had been on an "escape weekend" when a Rosalynn Carter aide called him to do Mrs. Carter's hair. But he was near the phone when Mrs. Reagan herself called and asked him to fill in for Julius, who comes to Washington once a month from Los Angeles. Weir, whose bipartisan clientele includes Virginia Knauer, Elizabeth Dole, Jeannette Williams and Marlene Stone, has done the first lady's hair three times so far, including the times before the recent white-tie diplomatic reception and luncheon honoring Korean president Chun Doo Hwan.

Unlike President Reagan, Julius is not quick to boast about his age, which is about half that of the president. "I hate numbers, particularly when it comes to my age or my fees," he teased. But he admitted that he used to adjust his I.D. to keep the age on his driver's license at a youthful number. "Now those computers ruin everything," he said.

The only one who "protects" her age more than he does, says Julius, is his client Zsa Zsa Gabor. He sent her 2 dozen helium balloons for her birthday recently just so she wouldn't forget the day.

While in Washington this trip Julius fixed Nancy Reagan's hair for a Vogue magazine photo of her wearing her Galanos-designed white-beaded, one-shouldered inaugural gown. But unlike the night of the inaugural ball when Mrs. Reagan wore her hair pulled back into a hairpiece, a style the hairdresser and his client created together, Mrs. Reagan wore her usual hair style. "That's the way the magazine wanted it," Julius said agreeably.

Before returning to California and at least one more birthday party, Julius will stop off in New York to pick up some birthday presents at Bergdorf. In fact, it is three of the same item, an argyle sweater he had spotted in Bergdorf's catalogue and hinted about to clients Mrs. Jack Benny and Betty Wilson (he said he can't remember who the third one is from). He fully expects to be disappointed. "Nothing ever looks like it does in pictures."