Opaque is not a color but a state of presentation where a colored object is depicted in such a fashion you cannot see through it, though the object is transparent in nature.  An opaque object is neither transparent (allowing all light to pass through) nor translucent (allowing some light to pass through).  Opaque can be on any color but its mostly done on clear glass which is transparent or see through and with a technique it has been made such that its no more transparent.