Pickled garlic turning blue or green is a common phenomenon, and while it may seem unusual, it’s completely harmless. This color change occurs due to a natural chemical reaction between the garlic and the acidic substances, such as vinegar, in the pickling solution.

Garlic contains sulfur compounds, primarily allyl sulfides, which are responsible for its strong aroma and flavor. When garlic is pickled, especially if it's freshly harvested, the sulfur compounds can react with trace amounts of amino acids in the garlic. These reactions, combined with the acidity of the pickling liquid, can lead to the formation of sulfur-containing compounds called sulfur ions. These compounds can cause the garlic to turn a bluish or greenish hue.

This color change is more likely to occur with young or freshly harvested garlic, which has higher levels of certain sulfur compounds. Additionally, the type of vinegar used can also affect how much discoloration occurs, with some vinegars causing more pronounced color changes than others. While the blue or green color might look strange, it doesn’t alter the taste or safety of the garlic. The pickled garlic remains perfectly edible and retains all its beneficial properties.

In summary, the blue or green color in pickled garlic is a harmless reaction caused by the interaction between garlic's natural compounds and the acidic pickling solution. It's a natural process, and the garlic is still safe to eat and enjoyable in flavor.