My suggestion is that you go into the SherwinWilliams store. Find the color that is closest to your idea of gray. Have them make up a sample. Take it over to the house and try it out on a wall. I am presuming the wall color has not been chosen yet. Look at it at different times of day. If the electric is on turn on the lights and look at it at night. People can go through a lot of samples trying to find the right one. Once you find your perfect gray you are done. If you chose a dark gray, use that on the island. Have the paint store mix it at fifty percent for the perimeter cabinets. I do not think they can make a sample that way, but if they do get a sample. If not buy a quart. Be aware that a full gallon may not be exactly like the quart you buy. It should be close though.

I did try to find you some nice gray pairs and I did not do well. I'll show you some of what I came up with.

Trying to match a set of grays made me more convinced you will not get a good pair unless you do them from the same gray color.