Is there an expression "white and black"?
In this case, "not everything is black and white" simply refers to dogs seeing more than just black and white colors, even though they are colorblind. However, the expression "black and white" is an idiom in other contexts and means that everything is clearly defined and there is no confusion or ambiguity. Ex: Love isn't always black and white. Sometimes there is confusion in a relationship. Ex: Don't try and make excuses, my instructions were black and white so you shouldn't have been confused.
Get more Native English Expressions >