Don't worry, it's normal for goldfish to change colors a bit. The goldfish I have now used to have black spots when I first got him, but now he is orange and white. Here are some pictures of him http://www.flickr.com/photos/31481877@N06/3010073802/ http://www.flickr.com/photos/31481877@N06/3010073774/in/photostream/
I must say that 3 goldfish will not survive in a bowl for very long. Goldfish produce a lot of ammonia which is toxic to the fish and will build up quickly in a bowl. Also goldfish grow to about 1 foot in length and can live for more than 10 years (sometimes 20 years) if properly cared for. If they are small (2 inches or smaller) they would be ok in a 20 gallon tank minimum right now with a good filter and will eventually need a 45 gallon tank with a filter. Goldfish are not meant to live in bowls, the only fish that can survive in bowls are betta fish, and that's only if the water is changed every week and it is heated. No other fish will survive in a bowl for more than a few months, it will stunt their growth (the body stops growing but the organs don't, causing the fish a painful death) and the ammonia, nitrite, and nitrate levels will kill your fish.