I think it's actually pretty common for the bulbils of garlic to be more purple or darker in color than the actual cloves. Back when I got my rocambole bulbils at the farmers market, they were almost brown despite the actual bulbs they came from being mostly white (with a pinkish cast on the inner layers)
I always assumed it was a function of how much light the tissue was exposed to (remember that, for a lot of plants, purple coloration is sort of like their sunscreen). That could still be the case here. These bulbils were ensheathed in the leaf tissues as they grew, but those tissues are still above ground and a lot more light permeable than the actual soil is. Certainly I know that for a lot of my garlic base, bulbs that have their bulges above the ground (either naturally, or through me having dug around them to expose them in order to check on their progress) are often VERY purple (many of my smaller rounds used to come out of the ground more or less the same color as a skinned red onion.)
