Male and female blue jays are the same color.

It is quite easy to differentiate male and female birds because, across most species, the male is a different color to the female.

However, blue jays are the same, making it difficult to identify whether they are male or female.
This is known as sexual monomorphism.

For blue jays, the easiest way to tell them apart is that males are usually larger than females.

The other way is through courtship. Usually, there will be one female surrounded by males who will follow and mimic her moves.