the colors on top of lead are for the most part oxidized metal. Pure lead will usually have a sheen of red blue or gold depending on the temp or the melt. Alloyed metal will have less color but will show it if you get it real hot. The silver scum on top is oxidized impurities and a little bit of oxidized tin and antimony residue. The Gold can also be a small amount of copper in your melt. The copper can be removed by shutting off your pot and waiting till it cools as it will float to the top and can be skimmed but ive never reallly saw where it hurt anything. I have tin based babbit that has a trace of copper in it and i did some testing with a and without it and dont even bother removing it anymore. The minute amout of tin and antimony that will oxidize on the top of your pot isnt worth worrying about either. I find that getting carried away trying to flux it in is more harmful to making good bullets then just skimming it off.
