Here is one persons take on improving skin tone in Picasa: www.informit.com/articles/article.aspx?p=418012&seqNum=4
Improving Skin Tones with Warmify
Picasa’s Warmify effect adds a slight orange tint to the image to make skin tones look better. Skip the Warmify effect completely—you have more control in the Tuning tab when you drag the Color Temperature slider to the right.
Warmify with one editing click