Same color as the trim, white. They should blend in and are not a design element on most houses.

Gutters come in a small number of colors, most of which aren't true matches for the body color. Cold vs warm whites, etc. Mostly we paint.

Definitely white. I prefer the baked enamel finish it comes in for durability, especially in harsher climates. Our roofer had sample color wheels with about 8 shades of white across two vendors.

I do gutters to match the soffit/fascia and downspouts to match the house wall color.

I also like to stick to the factory finish if possible.

For the majority of homes, gutters are a functional/utilitarian element and should not be highlighted.

What is going on with the shutters on that right garage?