“They clothed him in a purple cloak”
They dressed Him in a purple robe, twisted together a crown of thorns, and set it on His head. And they began to salute Him: 'Hail, King of the Jews!' (Mark 15:16–20 BSB)
What it sounds like today
Random cruelty with props.
The cultural key
Not random but a complete mock coronation, item for item: the soldier's scarlet cloak stands in for royal purple; the plaited thorns for a ruler's wreath or radiate crown; the reed for the scepter; the kneeling and 'Hail, King of the Jews!' parody the 'Ave Caesar' acclamation. A whole cohort stages the investiture of a client king, as barracks theater. Games mocking condemned prisoners as kings are attested in the period. Mark says purple, the actual royal color (murex dye, worth more than gold by weight); Matthew says scarlet, a soldier's cloak standing in for purple. Two memories of one improvised costume, both painting the same mock coronation.
Recovered meaning
Matthew lets the mockery tell the truth the mockers can't see: robe, crown, scepter, homage, royal title: every element of a real coronation is present and, on the Gospel's terms, valid. The soldiers crown the king while laughing at him.