You say that you do not see racism in the tech world. If it isn't happening to you, it can be very hard to see. Just as I did not see the sexism in the tech world until the James Damore essay blew up at google and we finally prioritized listening to women's stories. And then (after a lot of personal work I did with the help from my caring female friends) it became clear.

So perhaps you do not see racism because you've assumed its not happening, and because it's not happening to you? From what I know about racism (as a white person), it must be impossible that the tech world is simply free of racism. It's just hard to see when you are not the victim. The answer I've found is to listen to people of color when they say they experience racism. Don't challenge each assertion, take it to be true and then look further for corroborating stories. You will find them.