I took some screencaps from Merlin (1998) after we homestreamed it a couple of weeks ago.
Gawain in green is a sensible costuming choice.
In the succession argument scene, he ends up knocking Uther-body out of position while insisting that Lot should be king. After he demands Arthur to give a demonstration with Excalibur, he’s thoroughly convinced even though it means campaigning against his father. Everything turns out well in the end though!
I rather like the plaid he’s wearing on the field. Pretty sure I can reasonably call his helmet a ridge helmet, though the cheek guards aren’t very secured – too floppy. His shield device isn’t anything fancy, just a pointy tryskelion. The vid quality doesn’t help distinguishing the brooch he wears in his first scene, but the tourney for queen’s champion definitely is a sun motif.
Arthurian Legends 