This is an excerpt from a post Uny did on garlic "tincture" and why there may be color changes:
And don't be surprise if the color changes to a glowing/neon turquoise/teal blue! YIKES! The first time that happened I though I was in the middle of a chemistry lab gone berserk!! A quick google search "garlic turned blue" yielded the answer. Any trace amount of copper will cause that reaction, and sometimes just the chemicals in the garlic when added to other substances will cause it.