Colors are impossible to guess on monitors if you want to get close take this picture to the paint store and try to find a sample close to it. keep in mind that color can look very different in your space .

Yes, thanks
my lighting tends to make everything look yellow, however after
painting my downstairs BM simply white it looks way better.
Ive just fallen in love with these blue draperies for an upstairs guest room.
Love how they look with those white walls....

What a lovely room! (Pics like this make me want to redo my whole house. :)) On my monitor, the white walls are cool/neutral so look at BM whites like Chantilly Lace, White, Decorator's White, Cloud White, etc. Simply White has yellow in it so test it in your upstairs room to see if it behaves as it does in your downstairs. In any case, if the yellow shows, blue and yellow make a nice pair.

If your lighting makes everything look yellow then change the lighting to all LED bulbs in 4000K or daylight.

Thank you Patricia, will do!

Tartan, Was also thinking Chantilly Lace !

Designer White by Pratt & Lambert

https://www.coastalliving.com/homes/idea-houses/coronado-showhouse-room-tour?slide=153646#153646

Dovefeather by Pratt & Lambert was also used in the entry

https://www.coastalliving.com/homes/idea-houses/coronado-showhouse-room-tour?slide=153604#153604

The idea of changing light bulbs is a good one but you might want to do a bit of research when it comes to LEDs. They can be tricky to get right. I've had bad luck with some brands with their 4000K making the room look like an OR. I forget the brand that's highly recommended here. Philips' Hue range? Anyway, just a heads up. (Gosh, that's a pretty room! Blue and white with touches of green are SO classic.)

ETA: I've got Chantilly Lace in my SW exposure office and it's lovely, especially in the winter when it turns to snow on the walls in the afternoon. :) What exposure is your guest room? Don't forget that outside elements will affect white walls so it you have a large tree outside your room's window, any white might take on a green tinge.

Tartan, my GR faces north, but its south florida and lots of light.