First of all, who is paying for this house?? Why aren't your wishes being followed. If it's done, paint them..... https://www.bobvila.com/posts/213975-paint-marble-window-sill?page=1

I’d reverse the color scheme. Light trim and eaves. Add some trim to the bottom windows. And if you aren’t afraid of color, I’d pop the front door with maybe something in the coral/pink to orange range.

Oh Lordy! There’s probably a hundred shades of white paint. Your best option is see if you can scrape a paint chip off the sill and take it to your local paint store. They may be able to match it close enough. The other option is to go to a paint store and find the paint color cards. Pick as many as you can, bring them home and see which ones match as close as possible. Once you pick the right color, go back to the paint store and buy a quart of that color. You should be able to buy a quart of primer there too. Also buy fine grit sandpaper and a good brush for applying water-base latex. Any brand of paint will do. However, if the original paint is oil base, then you will have more work to do. You can’t apply water base paint over oil base paint without first sanding the entire sill and applying a primer.

You can have bright white windows and off white siding easily. Note that the same bright white was used as the trim color for the roof and entry to make it all tie together.