noun
faded from washing; washed-out
Describes clothing or fabric that has lost color or become worn-looking due to repeated washing. Often used for a comfortably worn-in look.
このジーンズは洗いざらしで、いい色合いになっている。
These jeans are washed-out and have a nice faded color.
洗いざらしのTシャツが好きだ。
I like washed-out T-shirts.
色あせる is a verb meaning 'to fade (in color)' generally, while 洗いざらし specifically refers to fading caused by washing.
Compound of 洗い (washing) and 晒し (bleaching, exposing to sun/water), from the verb 晒す (さらす). The combination refers to the faded, worn appearance resulting from repeated washing and exposure.