We have a sewer gas leak coming from out bathtub drain. The apartment maintenance crew will be here early in the morning to look at it, so for tonight we filled the tub with water to keep the smell from over running the house. The water in our apartment has always been very clear and pretty, but all the water in the tub is now turning a shade of sapphire blue. Is this caused by the sewer gas? Or should we be worrying about something like copper to? This is the first time it has ever happened to us since we moved into the place a month ago, and we are a little lost.

Your snell could be rotting hair in the tub shoe,(see image) or it could be that the trap has lost the water sealI. If the maintenance crew can't locate the problem then try this.
Tonight before you go to bed pour 1/2 gallon of bleach down the tub drain and let it set overnight. Next morning flush it down with a few large pans of boiling water. ( This is important) The bleach will start to dissolve and soften the hair and make it slippery and the boiling water will melt the grease and flush the mess out into the main. Now see if that smelly drain doesn't smell sweeter? Hope this helps . Tom