I'll still pick up the Brightside color card in the next couple days but...
the Brightside green is not the same color at all as the Buick in your picture. The verde green on the Buick has an Olive tone to it. Definitely not the case for Brightside green. If you're just looking for any green to somewhat match the jams, trunk and hood underside, etc. then I guess it would be sorta OK.

If you like that Verde Green color and want to keep to something pretty close to it, I think you're going to have to experiment with mixing your own color.

Here's a decent video which shows you how to systematically arrive at your desired color:
http://www.baa-direct.com/Day3Course.html

...OR... Just had another thought. Somewhere in this extensive discussion it was mentioned that the Ace Hardware rust covering enamel paint is the same thing as Rustoleum AND that Ace Hardware will do custom color mixing. I imagine these stores have a color scanner which figures out the mix. So, if you can find a sample of the color you want -- you could take it to an Ace Hardware and get it mixed exactly. The advantage of doing this (vs. trying it yourself) is that once you get it right, they will also supply you with the ratios of pigments used in the mix -- so you'll always be able to have it duplicated later.