My son chose green for his fourth birthday. We made pop up frog invitations from green card and asked everyone to wear green. Party food was easy. Pin wheel sandwiches with cream cheese that had a drop of green food coloring added. Celery and cucumber sticks and potato chips to dunk in green tinted mayonnaise. Fruit salad set in Green jelly. Lime flavored milk shakes with green straws. A frog birthday cake. Lots of green jelly beans, wine gums, lollipops, jubes, etc. Decorations were light and dark green balloons and streamers. Games - we painted a big green monster and the children had to stick on his nose (as in pin the tail on the donkey), pass the parcel using varying green papers on each layer. Party bags included a simple, inexpensive but fun toy frog that when squeezed flicks out its long tongue and chocolate frogs. Any color can be chosen and with a bit of imagination food and games etc, can be adapted to suit.