I think the dyed hair (and also earrings) is used as a device to emphasize his personality
You're missing the point, japanese live action are often the reflection of the manga adaptation. They just want to make the adaptation is as close as the original. You tell me why they keep zoro hair green?
That scene when Leon and Fiat caught Leo and Pob together is so cringey. I believe that episode 5 could be written better, but they are so eager to sell LeoFiat Sex life.
https://youtu.be/QYYOk7N2U00