You clearly did not research this, because your title is false. Project Implicit itself acknowledges some people show biases for other races than their own, and some show no bias at all.

Also:

"A quarter of all whites demonstrated an implicit bias for blacks, and a similar share (27%) was race-neutral."

https://www.pewresearch.org/social-trends/2015/08/19/exploring-racial-bias-among-biracial-and-single-race-adults-the-iat/