I thought the red really worked because - okay, this will take a little longer to explain.
I imagined all the pictures from this series next to each other in a gallery. (I don't know if they've been exhibited.. they should be, if not!) And this one is called "End" so I imagined it last.
Why red? Well, all the other pictures, you look at from the side - the cyclists, and the painter, it's like they're all underwater and floating. In this one, we're definitely looking DOWN at her, and she's fallen... the dimensions are totally different. It's a bit of a shock, visually. And her position together with the title suggests death, which I think the red colour underlines better than the blue.
Then again blue would be more subtle and fit together with the others better visually. But red is definitely more of a shock.