Start with Soft Lavender on the walls and the whole room goes quiet. It is a pale, dusty purple with just enough gray in it to read as soothing rather than sweet, which is exactly what you want where a baby naps. In morning light it leans cool and airy, and by evening it settles into something warm and tucked-in. It is gentle without being plain, so the room still feels like it was chosen with care.
Wrap the trim and doors in Warm Gray to give those lavender walls a soft, grounded edge that never competes for attention. Then bring in Muted Plum as your accent, on a crib, a chair, or a stripe of bookshelves, to add a little depth and keep the palette from floating away. Walls in the lavender, trim and frames in the warm gray, and one or two plum pieces tying it all together.