The shirt is a clue
In indoor volleyball, a libero is a defensive specialist who wears a jersey that contrasts with the rest of the team. The different shirt is a clue to a different job.
If five players are in blue and one is in yellow, that player has probably not wandered into the wrong team photo. Look for the libero.
Keeping the rally alive
The libero specialises in receiving serves and defending attacks, helping the team keep the ball in play. Think of the player rescuing a fast ball so a teammate can make the next touch.
USA Volleyball explains that liberos can replace back-row players without those changes counting as regular substitutions.
Different job, different limits
The FIVB’s international rules allow only one libero on court at a time. A libero cannot block or attempt a block, or complete an attack when the whole ball is above the top of the net.
Under those rules, a libero cannot serve either. Some US rules allow serving in one rotation position, so check which competition you are watching.
Watch the first touch
The next time a rally begins, watch the contrasting shirt before following the ball to the net. A well-controlled first touch can be the quiet start of an exciting attack.
For another sporting colour clue, discover why football cards are red and yellow.