Jar Jar wears this throughout most of the movie as his main representative outfit.
The costume consist of a dark, brick-red gown with long sleeves gathered at the cuff. The sleeves have horizontal brown lines on the lower part of the sleeve. The gown has a ribbed, diamond patterned texture to it.
Over that is a flowing, multi-color robe in dark brown, with a dark yellow – light orange and light blue pattern. On top of that he wears a brown shoulder piece with gold stripes and beaded tassels hanging down from all around it. The beads are (at least) three different colors with dark yellow – dark orange, light blue, and dark brown between them thus matching the colors of the robe.
He also wears a necklace with five Naboo symbols hanging vertically from it.