If you like the more natural settings, choose colors that compliment the surroundings. This is the perfect time for the boho look and floral prints.  Yellow and Royal blue are a couple of my favorite colors when shooting with grass and trees that are green.  If the grass is less than green, like say in the fall or mid summer, jewel tones work wonderfully and pop against the dull colors. Put away the high heels, and bring out the boots and wedges.