-ish: This creates an adjective meaning "slightly white" or "having a white tint". For example: "whitish" (slightly white).
-y: Similar to "-ish", but can also indicate "resembling white" or "made of white material". For example: "snowy" (resembling snow, which is white).
-ness: This creates a noun denoting the quality of "whiteness". For example: "whiteness" (the state of being white).
-ed: This suffix is used for past participles, and can be used to describe something that has been "whitened" or "made white". For example: "whitened" (made white).
Ultimately, the best suffix to use depends on the specific meaning you are trying to convey.