If my upholstered bed is in front of my window...

[Karbea]

Would it look better if the head board and blind are in the same fabric. I was thinking at night it could look great (when the blind is closed), or would it look too much?

I think that the headboard fabric being stretched due to upholstery and the blind fabric being looser, it would look a bit odd.

Does the bed have to be in front of the window?
Avoid red fabrics as they will fade in strong sunlight.

... you will be cold at night.

IMO.

id say contrasting colours the best

Yes I does have to be in front of the window, it is already, but we've curtains and they're a real faff to pull, so I'm thinking a blind will be easier.