Google is testing a new colored pin within the map that displays in Google’s local 3-pack. The test shows one of the icons blue, while the remaining are marked in the usual red.
Here is how it looks:
The reason seems to be that Google is showing blue for the result with the higher relevancy for the first result listed in the local 3-pack. It is hard to know whether the blue map icon would actually make a user think it is the best result though – a green icon might be a better one to show for what Google sees as the top local result in it.
Here are some more examples:
This seems to be a limited test as I was unable to replicate it.
Thank you to Sergey Alakov for sending the screenshots to The SEM Post.