Ninety minutes after Phil Morris enters the makeup room at CBS-TV in Hollywood, the handsome black actor has been transformed into a white man. The brown wig and moustache are in place, affixed with spirit gum, and Nick Schillace, the head of the makeup department, puts finishing touches on Morris' face, while Mark Landon, Nick's assistant, works on Morris' hands. The mood is jocular.

"Make a fist," Landon instructs.

"I know how to make a fist," Morris cracks back. "I'm an angry young black man."

"Not anymore," says Landon.

"That's why I'm angry," says Morris.

Morris, of course, is not angry at all, just enjoying his work. He has been on the daytime soap The Young and the Restless for 13 months now and is currently involved in one of the most unusual of all the fantastic soap opera storylines. He is playing Tyrone Jackson, a black law student who goes undercover as a white man, Robert, in order to infiltrate the Mob.

Morris says that it's no harder to play a white man than any other character. "I grew up in Beverly Hills with just about every class of white person there is, from Valley to beach person to Oxford preppy types to white trash, whatever. So it was pretty much right there at my elbow," he says, and adds, "I'm not so quote unquote black that it would be a real stretch for me."

Professional permutations of character should come naturally to Morris, 26. He is the son of Greg Morris, 50, of Mission: Impossible lame. Phil admits that while growing up he resented implications that he would try to follow in his father's footsteps. Today his perspective has changed. "It's a lot less stressful," he says of his career as an actor, "when you know that somebody else has been there before and it happens to be your old man."

The second of three children (sister Iona, 28, is an actress; Linda, 23, is a singer), Phil remembers that as a child he wanted to be a traffic cop. "It's power," he explains. "I knew this guy could put out his hand and stop traffic. I think it's my dream to be a director someday."

Phil's mother, Lee, wanted him to go to college "so badly she couldn't talk to me for a while." But after graduating from Beverly Hills High School he chose instead to take a job as an extra in Greg's never completed 1976 film, Com-Tac 303. The experience hooked Phil. "I spent six weeks in the Mojave Desert with my dad, Billy Dee Williams and Henry Fonda, having the time of my life," he explains. "I ended up really enjoying being in front of a camera." He subsequently moved on to TV roles in Vega$ (which, not so incidentally, co-starred Greg Morris), Hart to Hart and Hotel, as well as a part in Star Trek III: The Search for Spock.

Morris has been married for nearly two years to Carla Gittleson, 26, who is white, an old friend from high school and an interior designer. On April 5 they became the parents of a son, Jordan Michael.

Carla is happy about Phil's role as Robert. "My friends ask, 'Does he really look white?' " she says, but adds, "If I had a real problem with whether he looked black or white, I probably wouldn't be married to him."

Response from fans (Morris gets 100-150 letters a week) also has been encouraging. "I have not gotten any negative response from blacks or whites," he says. "But people do mention that they like me better black than white, and thank God they do!"