Sculpting with light means planning for the unexpected, says artist Larry Bell.

His newest work, two minimalist red-glass cubes that playfully reflect and refract light, have been installed on the Museum of Contemporary Art’s plaza.

And light is, indeed, a wild card. The glass structures, each varied shades of red — “habanero,” “hibiscus,” “carmine” and “cerise” — morph in transparency and reflectiveness as the sun shifts in the sky.

At noon, with the sun blazing directly above, the cubes are intensely animated, each a shimmering box-within-a-box casting dramatic shadows that change shapes and positions throughout the day, like a sundial. They crisply reflect the urban surroundings — visitors rushing by on foot, water gushing from a nearby fountain, cars on Grand Avenue — as if wrapped in flickering film screens.

At dusk, the work mellows, taking on a stiller, more luminous quality, ensconced in a hazy, ethereal glow. It swallows up all those surrounding reflections, leaving faint, ghostly outlines housed inside. Shadows on the ground stretch and shrink. It’s as if the work were a great big, needy, living beast.

“It’s pretty amazing what happens at certain times a year,” Bell says. “When the sun is going down and there’s just a sliver of light that comes from the sunset through two of the towers that are there, it’s magical.”

MOCA commissioned the piece, called “Bill and Coo at MOCA’s Nest,” specifically for the plaza. It was a gift from museum trustee Carol Appel and her husband, David Appel. The sculpture is the seventh and largest Bell piece in the museum’s collection, and it replaces Nancy Rubins’ massive, more frenetic-looking sculpture of salvaged steel airplane parts that anchored the space since 2002. The Rubins work has been relocated to MOCA’s Geffen Contemporary satellite space in Little Tokyo, where it will debut mid-October. MOCA Director Klaus Biesenbach said he’s planning to build an outdoor sculpture garden there.

The Bell piece is the perfect work to mark the museum’s plaza, Biesenbach says, as it references the ‘80s geometry so prominent in MOCA architect Arata Isozaki’s building exterior. (Isozaki was awarded the Pritzker Prize this year.) Bell’s square sculptures fit right in with the building’s raised-pyramid skylights, the half dome over the ticket booth and rows of square windows. The warm reds in Bell’s piece blend with MOCA’s rust-colored Indian sandstone exterior.

“It really is in dialogue with the building,” Biesenbach says. “And Isozaki designed this building in dialogue with contemporary art. Our logo is a square, a circle and a triangle.” In that way, he adds, the Bell piece is also a nod to the museum’s founding artists as well as the Minimalist and Light and Space artists in its collection and the artists it exhibits today. “Larry Bell is an artist who’s represented in the collection, who was in the collection when the building was built, and now we circle back and show how beautiful that building is,” he says.

Even the Abstract Expressionists are reflected in Bell’s work. Just after noon, a familiar Rothko-like image forms on the side of one cube: gradations of reds, in decreasing saturation, appear on the glass panel, its bottom third divided by a fuzzy horizontal line.

The Venice-based Bell, a staple of the California Light and Space movement since the 1960s, is known for experimenting with surface treatments on glass that manipulate light, reflections and shadows. “Bill and Coo at MOCA’s Nest” is a continuation of a piece in the 2017 Whitney Biennial, “Pacific Red (V),” he says. Both works use his adaptation of an aerospace industry technique in which he applies thin metallic films to the glass.

The title of the new MOCA work is a nod to a 1948 film, “Bill and Coo,” which Bell saw in a Sherman Oaks movie theater when he was 7. The movie features a cast of professionally trained birds.

“I just liked the intimacy of the title. And the idea that MOCA was the nest for this piece,” he says. “It has the feeling that one has when you see these pieces — a very intimate, personal experience in the same way that billing and cooing are in a romantic sense. To speak softly and nuzzle.”

That Rubins’ sculpture and Bell’s new work are both flight-related is just a happy accident, Bell says. As are many of the unexpected ways that light and shadows play on the work.

“The best things happen by chance,” Bell says. “Spontaneity and improvisation and intuition are three of the most important tools in any artist’s studio. And the fourth most important tool is trust. You have to trust what you’re doing. I had trust that this was gonna work — and I was right.”