You can use the Effects tab of the editing window to change the appearance of your pictures using Picasa’s built-in filters. You apply an effect by clicking on the button that has a thumbnail of your image with the effect applied to it. This is meant to give you an idea of what the effect does.
To create a black and white image, click on the B&W button. You can also create a Sepia image, which adds an “old-fashioned” feel by changing the picture to a reddish brown tone. In all there are twelve effects that can be added with Picasa. You can undo the changes you have made at any time by clicking on the Undo button.
When you click on most effects, a set of sliders or buttons will be displayed so you can modify how the effect is applied.