I'm currently on my wit's end trying to find an answer to this that works for me, but every question and answer are referring to something different from my situation, and with most being Cycles-only across a variety of forums. I've a model here (extracted from a videogame) which already contains default vertex colours in its data. ^ Viewport view
And here is her hair in the texture, which was already grey-scale since the vertex colours do the job in their game.
Note that I've tried enabling Vertex Colour Paint on this character even in a new .blend with no nodes or anything else, but she remains the same. I also am not looking to accomplish this on Cycles; only Internal, like the title says.
This question in particular came close to the situation I'm in, but when they get to the actual answer, it's a dead end. How can I "bake" the vertex colours into the diffuse texture? I actually tried to search up on this as well, but everything is either cycles-related or just does not answer what I meant. I also don't intend on using a game engine, my main goal is to render this model with its default vertex colours applied onto the diffuse textures and save the render as an image.