I purchased*6 zucchinnis and*3 yellow squash plants, being careful not to mix up which was which when I planted.* My yellow squash developed a fruit, green in color.* It appears long enough to harvest now, but is still green.* I've never grown yellow squash before... does it turn yellow on the vine, or should it start as yellow and is my "yellow squash" actually a green zucchinni?* I really doubt I mixed up the plants when I planted them, but maybe they were mis-marked at the garden center.