Our well water also has sulphur... will really smell like rotten eggs if it's been sitting in the hot water heater too long. We filled our donut with it last year. I didn't have the yellow color that you describe though. If I remember correctly, this is hydrogen sulfide. Treating it with chlorine and aeration should eliminate the problem... as well as constant filtering. One of the real chemists on this board can probably shed more light on this one. The combination of bleach and aeration should oxidize it and also cause it to gas-off. Hydrogen sulfide will break down to sulfuric acid. I can't remember what that will do to ph... someone else here should know. PH isn't a huge concern with that kind of pool.

hth