Usually you can tell red wine glasses from white by looking a the bowl shape. Red Wine glasses typically have wide bowls to allow the optimal air flow through the wine bringing out flavors you would not taste by drinking from a white wine glass. Red Wines are very aromatic and flavorful compared to the more subtle whites. Red Wine glasses allow you to get the most out of your drink.
As I said above, White Wines are subtle wines. Though they still have flavor, they do not have as intense of a flavor as reds do. Due to this, the white wine glasses have a much narrower bowl . This helps keep the temperature cool which is great for whites because they are usually served cold.