about the meanings of pirate clothes

The lookout in the crow's nest up on the mast of a pirate ship called out that she'd spied a warship on the horizon, heading that way. 

Captain said, "Bring me my red shirt ! (That way, if wounded it wouldn't show and the crew wouldn't be discouraged. (Nor would marinara sauce show, by the way.) )

After a bit, the lookout called out that there were now 12 warships on the horizon.

Said the captain, " Look sprightly and bring me brown pants !"