I'm with Thurg. I live in rural eastern Ontario, where there are still a few active Orange Lodges, and a large number of small decrepit former Orange halls in small hamlets, which are no longer used as such. I've never heard of wearing orange on March 17th as a "custom"--and I'm in a staunchly Presbyterian and conservative neighbourhood that takes great stock in pride in tradition.

I had a look through that orangenet website linked above. Interesting stuff if not exactly forthcoming. They present the Orange Institution as an alliance of conservative Protestants of various denominations,who give lip service to tolerance of other faiths, but enjoy "pointing out errors" in doctrine.

The bottom line is, St. Patrick's Day is not their day, is it?   
The Orange day is July 12th(?) the Battle of the Boyne. They celebrate "Unionism" with the British crown, and the Protestant religions. Wearing orange as a statement on Mar 17th seems like just pissing on someone else's parade.

W-O