Resolution changing render colours

I am working with old DV camcorder footage, which is 720 x 576 PAL. If I render them at this resolution and re-import them to the same timeline the colour has shifted, so that the reds are much more orange.
If set the project to 1920 X 1080 and use the same clip rendered to 1920 x 1080, the colours in the re-imported clip are identical to the original (with bonus black bars).
I would not expect the resolution to affect the colour. Am I doing something wrong?
If set the project to 1920 X 1080 and use the same clip rendered to 1920 x 1080, the colours in the re-imported clip are identical to the original (with bonus black bars).
I would not expect the resolution to affect the colour. Am I doing something wrong?