Looks fine to me, maybe the welds could do with a bit more rubbing down, but as you say it's an experiment.
Personally I love discoloured pipes, it shows that the machine has been used properly. If they were all pristine and shiny people might think it's a garage queen.
+1 from me, on both points! I suppose with a huge amount of polishing you could get them back to even bright silver all over and then let them discolour evenly...but just getting a few hours of proper running temperature on them should have everything blending in anyway. You do realise you may just have done one of those classic temporary repairs that is still working many years later!
