How soon was the tank set up before the fish was put in there?
This is pretty critical as your water may have some toxic chemicals in the water that are causing this fish's symptoms. Read this 'sticky' article quickly to better understand what I mean:
http://www.fishtankforums.com/5-fres...-aquarium.html
My instinct from reading your origonal question was that this may be ammonia poisoning and now I believe that is a good probrability here. I would do another water change tonight or as soon as you can at a rate of about 50% of the water in the tank. (The sticky article above will also help you understand why)
Are the red scales more close to the gill area?
From your last post, it seems like the fish's condition is worsening, but I wouldnt give up just yet. There are some people that can find ways to get past this and spare their fish's lives in the process.
By the way, I am glad to see that you are keeping this goldfish in something other than a bowl! You may also want to think about adding an airstone as this will help oxygenate the water. Keep in mind that it is not actually the bubbles that the airstone produces that helps with the gas exchange (CO2 out of the water, O2 in) but more so the aggitation of the water's surface. I dont know if you are running a filter on this tank, but many of them create the same surface aggitation effect. If you are not using a filter, then it may be wise to help promote gas exchange through the use of a air stone. The more aggitation (to a point, of course) the better, especially if you can do it throughout the entire surface area of the water.
Hope this at least gets you pointed in the right direction!