This is an acid-base reaction (neutralization): Cu(OH)2 is a base, HCl is an acid.
Cu(OH)2 – Copper(II) hydroxide
Other names: Cupric hydroxide, Cu(OH)2
Appearance: Blue or blue-green solid
HCl – Chlorane, Hydrogen chloride
Other names: Hydrochloric acid, M, Uriatic acid
Appearance: Colorless, transparent liquid, fumes in air if concentrated ; Colorless gas ; Colourless compressed liquefied gas with pungent odour ; Colorless to slightly yellow gas with a pungent, irritating odor. [Note: Shipped as a liquefied compressed gas.]