C7 Christmas replacement bulbs are available in a variety of colors, shapes, sizes, and wattages. The most common C7 replacement bulbs are 5 watts and come in a variety of colors such as red, green, blue, and white. Some C7 bulbs are even available in multicolor options. When replacing C7 Christmas bulbs, it is important to make sure that the wattage of the replacement bulb is the same as the original bulb.