Shouldn't have to Choose
I have completed a lot of research on racial and ethnic issues in the Dominican Republic as well as visiting numerous times with my Dominican friends. For people of mixed races, they shouldn't have to choose only one; that's an American mentality that needs to go away. I completely agree with what the previous writer said about mixed race children and "at what percentage are they in what race".
If someone identifies more with "Black" or African culture, fine, let them be proud of that part of their heritage, but if a mulatto feels more comfortable and identifies more with the white part of his heritage, that should be acceptable too. Most of my Dominican friends admit that they have Spanish, Arabic, French and African ancestry, but they do not consider themselves "Black" by American definitions because they do not limit their identity to only one part of their background. Their skin color, features, hair, etc. would not categorize them as phenotypically "Black" either.
My boyfriend is Dominican, and while he does not appear "Black", yes, he does have African heritage (which is more apparent on his mother's side) he is a mixture of so many things that I would not just tell someone "I'm marrying a black man"...I would say "I'm marrying a Dominican". Whites are allowed to claim their distinct backgrounds, such as saying "I'm German-American" or that they are part French, German, and Irish. Those of mixed race should have just as much ability to claim all parts of their background and not just be lumped into one category unless that is what they choose for themselves.
The whole "Indio" categorization does show some bias against their African ancestry in claiming that their color and features come from the Taino indians. However, this exists as a cultural myth, and while the Tainos may have been essentially wiped out in the early years of the conquests, Dominicans have a right to be proud of the Taino contribution to their history. The good thing about Dominican racial categorization is that it takes into account many factors, not just the "One drop" American rule.