Copper(II) hydroxide is light blue. It is rubbery when wet. When it is mixed with copper(II) carbonate, it is greenish. It reacts with carbon dioxide to make copper(II) carbonate when in air. It turns into copper(II) oxide when wet. When it is dry, though, it only turns into copper(II) oxide when it is heated. It reacts with ammonia to make a very dark blue solution.
Copper(II) hydroxide can be made by reacting copper sulfate with sodium hydroxide. Potassium hydroxide can be used, but it is more expensive. It can also be made by electrolyzing a solution of sodium bicarbonate with a copper anode.
It is not toxic in small amounts, but it can dissolve in stomach acid to make soluble copper, which can poison much more easily.