I want to use this image (well just the white man, not the blue background, but i'll cut that out in photoshop) and have him get filled slowly (from top to bottom or bottom to top) with a color (in this case, red).
Is this possible with after effects? If so, how?
If I need to, I could easily convert that picture to a vector graphic if that would make this easier/possible.
Since there's no image here, I'm going to guess. All you should have to do, once you have the man cut out in Photoshop, and imported into After Effects, is to use the man layer as a matte layer, create a red solid, then use a wipe effect to wipe the layer from bottom to top, or vice versa. The man layer will work as a mask to reveal only the red which is within the man outline.