I did a couple of google image searches for basque, basque art, basque culture and basque traditions. Lots of images of the people and flags and dancing and artwork. Definitely red and green (primary, think Christmas!) with lots of white and black accents. White shirts and black aprons and pants in the dance costumes.
Im not sure if the SE Oregon/SW Idaho basque culture has held onto the European basque traditions and heritage or not. My dh has family in that area and 2 cousins that married basque men, and aside from basque names they seem pretty mainstream at family gatherings. I don't know them well though.
Good luck!