Guess the countries whose flags have been color inverted to a negative image.
If desired, use the color wheel in the thumbnail to help identify colors - negatives are opposite each other in the wheel.
Black and white are negative to each other.
Thank you for your positive response. What you write about locking in on a color makes sense, but how time consuming is is doing that? I did struggle with choosing an appropriate amount of time for this quiz. Any feedback on that is especially welcome.