Hey!
I'm not the best with titles, but I'll try.
I don't know the scope of your PIP, and what exactly it entails. Have you explored specific races? Is it mostly focused on biracial people who are both black and white?
If your PIP mostly explores biracial people who are both black and white, and identity issues faced, maybe you could do something like:
"Too Black to be White, Too White to be Black" or "Too white and/or too black" which I feel is a common issue many biracial people experience, where they are excluded from either racial identity.
You could do something a bit more metaphorical, "The Grey Line between White and Black" or simply "The Grey Line"
Something more general for other biracial identities, maybe another sort of metaphorical approach, where you incorporate two opposing things, that are important to each other? e.g land vs sky, horizon meeting earth, water vs sand, hill vs valley etc etc
I feel like this shows the interconnectedness of the biracial identity, and that without one, their identity is in a way removed - water means nothing if it never meets earth, as there is nothing to differentiate it by. Hopefully this makes sense?
Like you could do, "Where Hills meet Valleys - An Investigation into.. etc etc)
If you want something simpler, maybe alliteration could work.
E.g "Beautifully Biracial"
You could do a play on words, "The B Word: An Investigation into .." (quite attention grabbing)
That's about all I got. Hopefully one of these appeals, or at least sparks some interest or foundation for your own creation.
Best of luck!
