Refers to the flowering plant Syringa vulgaris, known for its fragrant purple or white blossoms.
庭にライラックが咲いている。
Lilacs are blooming in the garden.
リラ and ライラック both mean lilac, but リラ comes from French while the more commonly used ライラック comes from English.
lilac (color)
Borrowed from English 'lilac', ultimately from Persian via Arabic and Spanish.