I don't think latex paint "yellows" over time. Sunlight can change the color of anything. Paint included. Over time the color of your woodwork will bleach out by the sun. Also, paint formulas change over time so 10 years ago the paint would have been formulated in a slightly different base. This changes the color so even though it says "Moonglow" or whatever, it is a slightly different color. I have found that when I keep some paint to do touch up it is really only good for a few years because then sun damage has changed the color and my touch up paint is "brighter." Good quality latex paint in satin or semi-gloss is the standard for interior woodwork. When I paint I paint everything at once. Then keep some of the paint (you can transfer it into a mason jar if you have less than a quart left at the end) for touch ups. If something gets badly damaged I might repaint a full door or baseboard. But in general, just keep touching up little nicks until it is time to paint again and don't look at it too closely! Good luck!

I think your ideas are right on for light fixtures and door colors. What I cannot get passed is the eyebrow trim over the garage doors and/or the lites in the garage doors. Too late to do anything about the curved trim but can you do without the lites in the garage doors? Should be an easy panel replacement.

The siding appears pale blue. I'd paint the siding, trim and garage doors white. Buy beefier front door light(s) in black and paint the front door black.

I would paint them black/or charcoal/or a very deep greyish/blue (per pic) and any of these should really compliment your stone/brick/stucco. When painting the front door, include the side lights as well which will make the entrance look more prominent and you could even add a knocker. If you don't already have one, a large light fixture (per below) does wonders. When planting your urns next year look to add various heights/different shades of green (lavender for example has a bluish green) and a potatoe vine (burgundy and green). In the Fall, I add birches, in winter top up with boughs, etc and in spring add pussy willows before the flowers can be planted - so they are full all season. I know it's doesn't sound like much, but they will add impact as well.