same color
Refers to two or more things sharing the same color. Often used in contexts like matching outfits, coordinated designs, or identical hues.
彼女と共色の服を着てデートに行った。
I went on a date wearing clothes of the same color as my girlfriend.
この部屋のカーテンとソファは共色で統一されている。
The curtains and sofa in this room are coordinated in the same color.
Compound of 共 (together) and 色 (color). The exact historical derivation is uncertain, but the meaning is transparent from its components.