Max - I'm not - completely - ruling out the exposure variable, but that leads me to new questions:
1) is that the same blossom, subsequent ones on the same spike or two different bloomings, or even two different clones? Culture can affect colors, with bright and cool usually allowing more red to develop.
2) If it IS the very same blossom, were the two photos taken with the same camera? Digital camera sensors have different spectral responses.
If your photos are of the very same blossom, taken using the same camera, with different lighting conditions, then by all means it's an exposure phenomenon. Otherwise, I doubt it.