You don't mention what color trim is in the master bedroom but if it works wth your tile selection, that's the easiest and most continuous way to go.

i think your best best with the wall color would be to have the paint store mix a sample quart in a half formula of Edgecomb gray. If that is too much color you could even go with 1/4 formula. Doing a decent sample (two coats!!) on the wall in the space itself will give you a good idea on color.

For "white" ceilings I generally use 1/2 formula of the trim color. Hope that helps.

If trim in MBr doesn't work, try White Dove. Without seeing the tile in person I can't advise as to whether it will work. I like to prime and paint a piece of trim (about 12" or so) so I can get a good idea of the color and carry it around with me.

White Dove is a no, go with a white that doesn't have obvious tones jumping out at you (yellow, pink) when you compare the tile and paint side by side. Again, working up a trim sample is always better than choosing off the paint chip.

Try Cotton Balls (OC 122), Cloud White (OC-130), or Decorators White

In my bath it is just the opposite -- the tile and wallpaper background are a cream, but I painted the ceiling and trim with basic "kitchen and bath white" -- and it looks pretty good to me! It matches the white porcelain sink; and is not a stark white but still a fairly pure white (no discernable undertone color)

Agreeable Grey Sherwin Williams

Have you used this with subway tile?

Is there a pic of what you ended up doing? I'm having the same issue, which white paint w/ white glossy subway tile?

Work with Edgecomb Gray and use a coordinate that's not white. Try Gentle Gray