I think I see some yellow in the stone and a light yellow would be more appropriate with this style house. Perhaps a blue-gray-green on the dormers to match the roof. Lots of white trim. In the 50s people didn't use much gray on these ranch houses.

I love the drawings you have posted - it looks like your project will be gorgeous in the end whatever direction you take! We love a flat wall, here is one we did for a client's basement. It is worth talking to your contractor to talk about the pricing for all the options. Cladding the wall in a quartz may require the framing to be reviewed in the wall to accommodate the weight and installation of full cladding.

I am also doing a kitchen from scratch, and have spent some time on this issue. I have been browsing kitchens and looking at three things: floor color, cabinet color and countertop color, and trying to ignore the other detail. It seems to me these are the building blocks of the room. There is a lot going on in a kitchen and that is a lot of color and texture, so ultimately I will use a kitchen design service, but initially I have discovered that the rooms that appeal to me have wood floors, either white or rather dark (furniture look) cabinets. If the cabinets are white, then you can go with a white countertop or one which coordinates with the floor color, such as a granite that blends nicely with your fir floor. If there are too many cabinets and you like some dark wood or dark painted color, you can add glass fronts, or lighter cabinets to break up the mass of dark color, often done on the upper cabinets. I would also keep in mind the artistic composition rule of "golden thirds". Eye pleasing arrangements have masses of color in threes, so visualize your kitchen as you enter it as a painting. It helps to squint, actually and try to see the masses of color. You can do this as you browse pictures. If the kitchen is monochromatic, the masses will appear more subtle, in shapes and textures. I think that the modern designs I see in kitchens are attractive because they seem to be composed of horizontal masses, or swaths of cabinets, whereas in your beautiful home, a more classic setting, the vertical will probably prevail, especially if you decide to continue the ceiling beams into the kitchen. Recognize this is a very strong design element, and introduces more to an already busy room. Not saying it can't be done beautifully, just that it will take careful planning to look just right. I think your instincts are correct about cabinet color, to contrast with floor. Otherwise, too big a mass of one color unless you have a lot of upper wall or window to balance it. The kitchen is also a working room, however, and personally, having lived with dark, medium and light countertops, I would rather work on a light surface. My eyesight is not that great and I find the medium and dark granite countertops hide too many spills, and were harder for me to keep clean. My favorite by far was my quartz composite that looked like marble, and one that was sparkling white. Ridiculously high priced, but easy and beautiful. If you don't have those issues, then you have more options for dark cabinets. But you should consider if you have strong preferences about other design elements as they may tip you one way or the other on the cabinet choice. I love the wall colors and your floor, hope to see some pictures as you move forward.

I assume you're asking for a color recommendation, and without having a piece of fir to test it on, there's no way anyone can give you an exact answer. What I would do is to buy a piece of fir at the hardware store along with some stains in the colors you like, and apply the stain to see how the color looks. You might need to apply a couple of coats to get the desired color. You should also apply a wood conditioner after sanding and before staining to close the pores on the wood so it looks better. We use the minwax one: http://www.minwax.com/wood-products/preparation/minwax-prestain-wood-conditio