No, opaque materials do not always appear to be white. The color of an opaque material depends on the way it reflects, absorbs, and transmits light.
Opaque materials are those that do not allow light to pass through them. When light hits an opaque object, some wavelengths of light are absorbed while others are reflected. The colors that are reflected determine the color we perceive. For example, a red apple appears red because it reflects red wavelengths of light and absorbs others.
Materials can be opaque in a variety of colors, including red, blue, green, yellow, and many others. Therefore, while some opaque materials may indeed be white, this is not a characteristic shared by all opaque objects. The perception of color in opaque materials is influenced by their intrinsic properties and the spectrum of light they reflect.