I'm not an expert, but I don't think that's right. The film is not exposed directly by x-rays. X-rays get emitted, pass through what they're imaging, and then hit a screen that glows in proportion to the x-rays that hit it. This screen either glows with green light or blue light, and that's what corresponds to the x-ray film being blue or green labelled. It's the glow from the screen that exposes the x-ray film. Both emulsions on a two sided x-ray film are the same, and they both respond to visible light, either blue or green (and perhaps more.) X-ray film is two sided since that leads to double the density, which is important when looking for flaws in bones.
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