Not sure, but that might be true more for ionic silver than actual colloidal silver. Grey and green colors in ionic EIS silver is indicative of larger particles, but at least when it comes to grey that is not true of true colloidal silver.
From the mesosilver website:
Once the bottle is opened the color of MesoSilver may change to gray depending on the atmospheric pollutants found in the air. This color change does not indicate a problem with the product and is not cause for concern. The effectiveness is not effected. The color change to gray is commonly found in large cities like Boston, New York, Chicago, Los Angeles, Detroit, Denver, and in many cities in California.
How odd. First of all it is odd because I have had many, many gallons of Utopia Silver Colloidal Silver and have seen thousands of gallons of it being made - and I would never describe it as gold. Dark amber perhaps, but really it looks more like strong tea. Once a bottle is opened it can change to a more greyish color. Once it was thought that they greyish color was indicative of larger particles, but that is only true for EIS ionic silver and not true for true colloidal silver such as is made by Utopia Silver and Purest Colloids (mesosilver).
Did you notice any particulate matter in the bottom of the container? My suggestion is to call Utopia Silver and tell Ben Taylor I suggested you talk to him - he may want you to return the bottle to check on it and replace it.
Now, here is another thought: what exactly is going to contaminate colloidal silver? Certainly not a pathogen!