April isn't black or white... She's a drawing.
As for this:
http://media.tumblr.com/ccffd6b46235...8gl1qmks9t.jpg
Yeah, there were tons of white girls who looked exactly like this in the 80s. Hair and all.
There's really no evidence that April was ever intended to be black, beyond some crappy artwork that could be seen either way and Kevin Eastman's random tall tales a few years ago back when he was in his major "Cool Uncle" mode and was saying anything and everything to seem hip and connected to the franchise. These days he's more normal.
And there's really no point in making April black. Randomly changing her ethnicity doesn't add anything to the character and serves no point. And if the point is to make a "strong black character" then you need to create one, not randomly change the color of someone. That's just lazy.
And the only medium this would likely ever happen in is film and it seems unlikely that's going to happen anytime soon. So this is just an excessive discussion in nothingness.