Such colorful family mosaics - Marcy called them "rainbow coalition" families - aren't new. White couples have for years adopted children whose ethnicity differ from theirs, often because more such children are available than white babies. Too often, say agency officials, black adoptive parents can't be found.

Though always controversial, "transracial" adoptions are getting a closer look, thanks to the Senate's consideration of a bill that says race can't be the sole consideration in children's foster care and adoption placement.

If the measure passes, agencies that prohibit or unduly delay such adoptions would lose federal adoption funds. The bill, sponsored by Sen. Howard M. Metzenbaum (D.-Ohio) and supported by such influential African Americans as Sen. Carol Moseley-Braun (D.-Ill.) and Marian Wright Edelman of the Children's Defense Fund, could come before Congress by Thanksgiving.

Critics, such as the National Association of Black Social Workers, say such adoptions wouldn't be necessary if agencies tried harder to find black adoptive parents. They fear that black children raised in a white milieu may not appreciate their heritage, culture and themselves as African Americans.

The Fosters say they agree, and that however many smiles they've received from black strangers since Dougie joined them, their home isn't optimum for a black child.

They say that for all their inclusiveness - prints of an African warrior and Martin Luther King on the walls, Dougie's ethnically diverse preschool and storybooks - there are things they can't give their son.

"I don't want Dougie to grow up to be uncomfortable (with other black men)," says Charles, haltingly.

"When I'm in a group of black men relating to each other, there's a different dynamic from what I grew up with . . . that I appreciate, but had no way of learning. . . . I want Dougie to feel comfortable with it."

So they've done what they can - hired a hip, young black woman to babysit, become foster parents to a long-lashed, black 2-year-old whom they'll also adopt if no black family can be found, and settled in a supportive, mixed neighborhood.

While such complexities might puzzle any 9-year-old, they truly bewilder Sean Foster because he is completely at ease with his brother's blackness.

When Marcy and Charles had trouble conceiving a second child in 1988, they opted to adopt a black child rather than "spend $20,000 to go to India to find a baby," says Marcy, who grew up near an ethnically diverse family. The Fosters soon located a teenager who was eight months pregnant and couldn't find adoptive parents for her baby.

The adoption was arranged by the Datz Foundation in Washington, D.C., whose screening included frank discussions about the responsibilities of raising a child of a different ethnicity. Says director Vivian Datoff: "Just raising certain questions can make couples decide they aren't qualified."

When Sean, then 4, learned he would be getting a new brother who's black, he was "excited" - for typical, little-boy reasons. "I just wanted a brother so I could fight him," he says. "Though sometimes I'm more gentle."

Dougie's skin color doesn't matter, he says. "Everybody is, like, a human."

He sighs. "My best friend at school is somebody who's black. . . . I love Dougie. I mean, the only thing he's scared of is bees."

Adds Dougie brightly, "And fireflies."

So much to fear. I share social workers' dread over the placement of African-American children - in a society that too often denigrates them - with families potentially unequipped to counter the negativity. That's why every effort should be made to find qualified black adoptive parents.

In a more perfect world, the worst thing a boy like Dougie would fear is bugs - never other people's judgments or perhaps, someday, his own doubts about having a white family. In a more perfect world, all parentless children would find same-color families to love them.

But in the imperfect meantime, I'm with Charles Foster, who says, "We're giving him a great advantage . . . the opportunity to feel loved for who he is. . . . You can pontificate all day long, but . . . these children have to be loved."

Actually, in a perfect world, such discussions would be moot. Everybody would be, like, a human.

(Copyright, 1993, Washington Post Writers Group) Donna Britt's column appears Thursday on editorial pages of The Times.