I'm sure your grandson and his bride will love whatever you make for them. However, keep in mind that they aren't quilters, so they will see this as an element of their bedroom rather than a stand-alone work of art. They might not want contrast - it will make the quilt less interesting on its own, but might make it fit with their room better.

I have made three different quilts for my own bed. The one that I find least interesting as a quilt is the one I most like on the bed. It's all light colours, with large blocks, and I find it very serene. The others with more contrast and more interesting patterns are less relaxing, so as much as I love them, I use them less.

Your grandson and granddaughter-in-law might not feel that way, but I would talk to them and see what their (and especially her) preference is. If they want low contrast, that's okay; they are just looking at the quilt differently from how we as quilters do.

This is an awesome combination. Perfectly modern look and great colors.

I would ask the bride for color hints.
But your daughter is the one giving the quilt, so she is your customer (sorta) and it is what she wants to give.
Good luck with the colors.
What Pattern are you thinking about?
Mike

One of the gals at the guild meeting showed a quilt that was done in grey and white (she called it a yawner but it was very pretty). She used the white to make orange peel slices and put various greys as 4-patches for the background. It would look great with the green and grey.

I don't worry about color values. I just put together whatever colors I like. Green and grey would be fine, if that is what they like.

I've seen the chevron design done in gray and mint green. Usually there is cream or white with those colors to make them "pop" a bit. Just as an aside--I recently made a requested table piece from shirts of a deceased person. It seemed too light to me so did the binding in a dark gray blender. It was just enough to spice up the design. Just a thought.

How about a drunkards path?

I agree. I have pink and sage in my bedroom and used to have pink walls. I would never wear pink. Colors you wear are different than colors you use in your home. Ask her what colors she's going to have in her house. If it's going to be a bed quilt ask what color the bedroom is, if it's a throw ask what colors the living room or den are. The quilt will be way more useable that way than if it's her wedding colors of gray and mint green but her house has browns, beiges and corals.

My niece took a picture of the bedroom walls after they painted their house. It helped quite a bit.