1. Chill 1-quart mold in freezer. Soften vanilla ice milk slightly; pack tightly into mold. Freeze until firm, about 1 hour.
2. Soften strawberry ice milk slightly; pack on top of vanilla ice milk. Freeze for 1 hour.
3. Repeat with chocolate ice milk. Freeze for 6 hours. Dip mold into cool water, then unmold bombe onto chilled platter. Freeze until serving time.