II'm not sure it is a good candidate for a colonial remodel. Sure, you can change the windows, add clapboard and add some dormer and fill in the doorway, but you will end up with a 70s house trying to be a colonial that doesn't look quite right because the proportions are all wrong, and you'll need to replace practically every window and redo a lot of structure..

Cape Cod houses are much smaller scale and Colonials tend to be more symetrical and less horizontal. I suppose with an architect and a lot of money, it can be done, but you will practically be rebuilding the house in the process. And please don't just stick on a broken pediment and some shutters or columns and call it good. That almost never works.

However, if you embrace the houses' rambling style, you could go Shingle or Prairie, or maybe sort of 1950s colonial rambler (The kind of house Lucy and Ricky moved into) with maybe a pinch of Tudor revival. These are sort of ancestors or contemporaries to the ranch and mid-century modern .Perhaps just adding some built-in planters under the ground floor windows and terracing the hill and adding boulders, grass, cascading vnes and some ornamental trees would really help to make the house look more traditional and welcoming.

Personally, I think the lines of your house are great as they are and a bit of lighter paint to the siding and a brighter door and some landscaping would look smashing. Worth a try before doing anything too expensive or permanent.

Prairie/Craftsman:

If that is too severe for you, then the easiest fix is to go Prairie: Add a pergola stretching from the garage to over the entry would soften it a lot and not cost a huge amount of money. It could also extend over the 3-car garage supported by brackets(although space is tight), and make a shaded front porch across the front. This combined with perhaps a planter infront of the one-story portion with some creeping juniper and vines would add a Prairie touch, which could be enhanced with some stained glass accents in the entry and perhaps some glass in the garage doors (perhaps inserts rather than replacements). I would make the supports chunky if you have space to work with the scale of the house. and have some nice long benches near the entry.

Wisteria or grape vines is a nice touch. Some window boxes on the small windows upstairs and the front garage windows with trailing vines would also be a nice touch for this style.

Shingle or Colonial Rambler:

This is more of a stretch, and just changing to windows with mullions isn't going to do it (and if you do, make sure they are the kind that is chunky and on both sides of the glass). These styles really require som sort of porch or canopy and the large windows would need to be redone as strings of smaller vertical casements or double-hungs, not picture windows.

Removing or reducing the recessed entry and adding small vertical windows to the first floor that line up with the second floor would make it feel much more traditional and colonial, but would require extensive structural change and may not work with the floor plan.

Unfortunately, It looks like you don't have much space in front for a portico or anything. That would limit you to a narrow canopy or pergola of some sort either supported by brackets or suspended by chains (something that was done on commercial buildings especially), or maybe a very shallow "porch" with some clustered supporting pillars (square preferably) around the entry. A type of port-cochere might be possible, or a deep drive-through porch the width of the third garage, especially if you use it for storage or seldom used vehicles. A pergola could work with these styles too.

Both would work with shingles--smaller square cut type for Shingle and a shaggier rustic type for the rambler. Rather than painting the brick,, or covering it up with clapboard (which sounds like a potential maintenance problem, especially if it traps moisture) I would consider staining it to blend in, or maybe mortar washing with lime stucco, or a similar material designed to cover 70s brick. The stucco would keep the texture of the brick but soften it and change the color. This is apparently quite popular in the South, where moisture problems and salt and snow are less of a problem. If you use shutters, just put it on a few accent windows and scale them so they could work. Do not put them on picture windows, and operable shutters always look the best.

It could work, but, it is a harder stretch and more costly to achieve properly, and takes a skilled designer and good contractor to pull off.

I've included some pics of each type for inspiration: I can see it in my head but I'm having trouble finding the right photos. Maybe I'll work up some sketches later.