Fourth of July picnics and barbecues are usually pretty informal affairs, but that doesn't mean you should skimp on table decorations. Quite to the contrary: The table is one of the most fun things to dress up! Color coordination isn't going to be a problem, so you really can't go wrong with whatever you choose to cover your tables.
If you happen to have an old picnic table lying around (or can buy a cheap one), there's no need for tablecloths; a few cans of paint will bring it back to life. You can go with straight-up red, white and blue, or get fancy and stencil stars and fireworks on it.
The easiest thing to do with any other kind of table is to start off with a plain white tablecloth and then embellish it. Try striped ribbon, glittery paper stars, crepe paper edging or a fabric runner with tiny paper stars dangling from the ends. If that sounds like too much work -- or you're having a very kid-heavy event -- just cover the tables with white paper, provide red and blue crayons and stickers, and let the kids do the decorating.
Now that the table itself is prettied up, it's time to shed some light on the party.