What you're looking at is an image of Pluto with heavily exaggerated color data -- like when you amp up the saturation on an Instagram. It's a bit hard to see (sorry) but one side of the "heart" is much bluer than the other. In fact, the left-hand side seems pretty beige-y.
This seems to confirm something that the NASA scientists suspected based on recent photos of the "heart" feature: It's actually two features. In the latest images, it looks like the left half of the heart is smoother than the right, the team said at the briefing. It's possible that some texture has been lost in the compression of the image, but it could also mean that one side of the heart is a different geological feature than the other -- they're just both very bright, compared with the rest of the surface.
Don't be too sad about the broken heart. It turns out it's definitely Pluto the dog, anyway:
A space-whale named Cthulhu? Sounds just weird enough. But if that heart does turn out to be one single feature, we think the New Horizons team should place the Cthulhu moniker there instead -- if you squint a little, you can almost see the octopus-faced ancient god standing in profile, his tentacles flowing in the breeze.