White

There's a picture of blue bedding and a picture of brownish grey bedding. What do you have? What about the flooring, the furniture? How much light does the room get, how big is the window, what is the orientation? What is the decor style? Can you send some pictures?

The same bedding, vastly different colours. Nice dog.

Get the hardwood in, before you finalise your choice of curtains.
I think something in the green spectrum though. Hows that sound?

Also if you're looking for more changes and additions, consider bed side tables, some lamps and art, and at the end, wall paint.

I'm off for now, it's night where I am

I would choose plain cream or white curtains, which will go with everything should you change the bedding, and will give the room a lighter and friendlier look than the gray. A self-patterned thicker material would be nice. This may sound counterintuitive, but with all the cool colors I would choose a carpet that also has warm colors in it, which I would repeat in accents like chair pillows, paintings etc. It gets rid of that jail cell look that I'm seeing in a lot of rooms nowadays that have nothing but grays, browns and beiges. Yellow would also look good with your scheme. A bedroom should be warm, welcoming and cozy.

Here is a suggestion, if you are leaning toward white.

https://www.houzz.com/products/sonnet-panel-white-84x40-set-of-2-prvw-vr~87760492 

I would add some pops of red around the room. Everything can't be blue/gray & white. I would keep it simple with the curtains & match them to the white of the bed spread.

Hi again. I see the bedding as a brown-grey, is this accurate?

What are your thoughts on adding a deep green or plum to the space?