I agree. Match or compliment the brick/fire box. Make this as seamless and unobtrusive as possible. That's the easiest way to prevent the eye from picking out "after thought" projects/fixes. Too bad you can't use the faux brick in this application. I would like to say "Koodos" for bring the fireplace up to code before listing. Not everyone would do that! What's the current flooring? Is that vinyl, laminate, engineered hardwood?

IMO blue/ grays are hard to work with if i have a client that has to paint before a house is completed i highly reccomend a pale grayed green it is much more neutral than gray and seems to work with everything. Sea Salt from Sherwin Williams is a good color it is not the same as BM sea salt.

IMO the stairs themselves should match the main floor flooring id not having the carpet. I like the handrail to match the stairs and without any idea of your style I do not have an opinion on the spindles at all.

Definitely get the mildew off the roof. I have mine done every four years to keep it clean. Costs around $400 for my roof. You'll be amazed at the difference it makes. Right now, you have no clear view of the color of your roof so hard to pick a trim color. If the windows are indeed vinyl, you can paint them but you don't want to go darker than the existing color. It will absorb the heat and could cause issues with the windows warping. Google painting vinyl windows and you'll see the cautionary advice when painting them. If they aren't vinyl and you're free to pick a color, I'm with those who say don't paint them dark. Once you clean the roof, you could consider painting the gutters a darker color. Beverly's idea of staining the driveway is a good one. Really softens the look.