Sago
Red would be very harsh, if you choose white or an off hate cream it will not compete with the curtains.
Or vibrant if you like things brighter.
I once fitted out a suite with vertical blinds and chose three colours - white, silver and navy.
I'd love that. I can imagine it would look stunning. I'm not sure why Blind sellers don't do more of this.
When we had our blinds fitted, the chap told us of a client who had bought a different colour for each room.
Fine, until you looked at the house from outside.....
That wouldn't bother me. I spend moments pulling up in the drive and then I can only go in a single room at a time but they are in the colour ways I want them. The only other people I would be trying to please are the neighbours who are free to do what they want to their houses and I won't judge them.