Hey Alexis,
Unfortunately, it looks like Light Mountain is playing fast & loose with the truth. If it's offered in different colors, then it can't be pure henna -- although there's some subtle variation in color from henna from different regions, they all dye red. Probably LM adds different botanicals to "turn" the color, but it's not very honest of them to claim it's pure henna.
Hbbg, I know you said you didn't have time to experiment, but
www.hennaforhair.com has a page with dozens of gorgeous color photos from people who henna'ed their hair -- and each one has the recipe that person used. It might save you some trouble. I would definitely encourage you to look into pure, body-art quality henna. Everyone I know who's tried it says the difference is amazing, not just in color but in the conditioning benefits, how easily it applies & rinses and so on.
www.Mehandi.com is the sister site to Henna For Hair and it sells very high-quality pure henna. I don't know if they will ship to Canada but it can't hurt to ask
ETA: Henna for Hair is just a really amazing general-henna-info site. The webmistress is doing her doctoral on henna and other herbal hair dyes. She might well know more about henna than anyone else in the world! I really recommend the site for anyone who's thinking about henna.