'twilight sky' is a correct and usable phrase in written English.
You can use it to describe the sky during dusk, when the sky is transitioning from day to night. Here is an example sentence: "As the sun set, the twilight sky filled with stars."
Vaughn looked into the twilight sky and could not find the ball.
The comet reached magnitude 1 and was a spectacular sight in the twilight sky, with an extremely broad tail.
I am walking through an alien forest under the pink twilight sky of a world constantly at war.
The image is of an empty space, half-caged, half-open, with a window looking out at a twilight sky.
The twilight sky has reached the moment when, if I could, I would break a shard from it to light my way in the darkness.
But while the branches are barren and the roads are empty in these images, the twilight sky is an intense blue.
His ethereal renditions of twilight skies could, arguably, not have been achieved via another medium.
The influence of Camille Corot and George Inness is evident in his later works, in which the softened forms and muted details of meadows and groves are set off against dusky twilight skies.
To straightaway center field, Wilpon -- and his patrons -- could see strollers along the boardwalk, bathers drying out on the sand, gulls plunging from violet-hued twilight skies and sailboats bobbing in the Atlantic.
After Confederate forces overcame a Union army detail at Fort Sumter in South Carolina, Church turned out a little rush-job called "Our Banner in the Sky," showing clouds and stars in one of his signature twilight skies taking the form of Sumter's tattered Union flag.
With color as a connecting element, Michael's photos of red-walled Prahran cafés and twilight skies over St Kilda show there was something transfixing about the city in this period.
