For a fail-safe off-duty option, you can't go wrong with this combination of a short sleeve shirt and olive cargo pants. You could perhaps get a bit experimental in the shoe department and complement this ensemble with a pair of white and black loafers.
White and Black Loafers with Short Sleeve Shirt Casual Outfits For Men
A short sleeve shirt and dark green cargo pants make for the ultimate relaxed casual style for today's gent. And if you need to easily amp up this look with one piece, why not introduce white and black loafers to the mix?