Since only one of the windows will accommodate shutters properly, I would skip them altogether.
I would add color through landscaping.

I would probably add shutters to the single and doubles. I was passing a house the other day and they had double windows but that house sure looked better with some adornment on those windows, even if they couldn't be working shutters.

I think something pale like a gray or beige, or a soft sage/olive type green, with a dark red door would be pretty.

Of course, if you change the roof color later, the other colors could be a mismatch.

Very cute house!

There are several sites online which offer free samples of their vinyl shutter colors. I've linked one below that gives you a 'deck' of all their samples free.

I'd put shutters up where the previous owners had them as I can see the siding has faded, and around two of the windows that I can see, it's darker where the shutters were.

Are those maroon shrubs below the windows on the right? That might be nice to link the landscaping colors to the house.

Here is a link that might be useful: Perfect Shutters Sample Color Chips

Darling house! I think red shutters in a darker red and a slightly brighter/lighter red door would be pretty and colorful on that house. Just make sure the shutters are wide enough to look right. When you do replace the roof, a weathered wood look color (not tan, but a dark brown color) would go best.

You can add lots of colors of flowers--- red, yellow, purple-- that will make the white house fresh looking.