Photo of green peach aphid nymph
Green peach aphid may be found along the midrib on the underside of leaves of a host plant. Mature aphids are about 2 mm long (ca. 1/16 inch), egg-shaped, and the color of the wingless nymphs and adults ranges from pinkish yellow to yellowish green. There are usually multiple individuals in a single colony.

Photo Source: Michael Bush, WSU Extension, Yakima, WA