The 30-918 is only available in black. The black finish was added to the spring plate by the manufacturer because it has an ingredient that makes it possible for the furniture manufacturers to powder coat the chair frames after they are assembled. The black finish will hold an electrostatic charge that attracts the powder. You can spray paint the plates with aerosol paint from a local paint or hardware store. You should be able to find an aerosol paint that will come close to matching the original considering most of the spring plate is not exposed.
Fiberglass Rocker Spring Plates do not have holes drilled. You will need to use the old spring plate as a template to measure and drill hole to fit your furniture. It is suggested that you use a drill press to make sure the holes are straight. Re-assemble the parts the same way that you took them apart. There should be a metal plate or washer between the bolt head and the spring plate.