I have had these white plastic chairs for awhile, they are looking worn out. I think they sell paint for plastic, but are there any other ways to make them look not so plastic .
You will probably want to try this: Take some sheets (that you don't need) in whatever color you need. Buy some, if you have to. Trim them to fit the chairs, and then tie them on with some fancy-looking ribbon. If your sheet job looks good and you want to dress it up, or if it just still looks bad, dress it up by tying a cushion onto it. You can use a cushion that is the same color as the sheet, or, (since most weddings have 2 colors) use the other color. If you're stretched for time, do the extreme and unthinkable- spray paint them! OK, really though, you will probably be able to find someone able to do this for you.
krylon spray paint for plastics comes in colors AND textures
what if you put cushions on them? i've heard of the paint, too - maybe they make metalic colors, then it would look like metal!