A 3MO is learning by observing (often, staring) what a human face and form looks like. As they learn, something that is different from what has been learned will produce surprise and/or fear. If a "white" baby only sees "whites" they will react to a person who is "black". If a "black" baby only sees "whites" they will react to a person who is "white". Just about anyone who is a parent saw their children do that (unless their family and close social circle is multi-ethnic).
My daughter lives in Xining, China (when she isn't "trapped" in the US by Covid). Westerners are much less common in Xining than in, e.g., Beijing or Shanghai. So she gets many interesting reactions from babies and young children who have never seen a Westerner before (and sometimes overhears amusing verbal responses from children and parents who don't realize she is fluent in Mandarin).
Babies reacting to someone who looks different is normal, not racism.
