The color of the Hydrated copper (II) salts is

The copper present in the copper salts has unpaired electron so it can show color. Or due to the presence of Cu (II) ions.Copper salts →  Bluish Green Nickel salts  → Greenish BlueChromium salts  → Dark GreenCobalt salts →  Pinkish/purpleManganese salts →  Light pinkFerrous salts→   Light GreenFerric salts →  Pale Yellow