Yes, I know it isn't Thursday. Those titles are more guidelines than actual rules.
PICASA NOTE: If you save a picture in Picasa, it saves over your original. You will need to make a copy of your pictures and then play with the copies if you don't want your originals lost.
You can leave a lot of color or like in the picture below, you can take almost all of the color out.
This is also my perfered way to make a picture black and white.