Another outdoor-decor problem? Not considering the more permanent fixtures when choosing a decor scheme.
I've been watching a home reno near my mother's house with interest - the owner chose a stucco colour that they thought would be a neutral: grey. Undertones are a tricky thing, though - the grey chosen has very strong purple undertones, which are brought out even more by the sun (the way your house faces has a big effect!)...so the house actually looks purple. Not necessarily a problem, and it can actually look great depending on what you put with it...but this particular house has a warm brown roof, and this particular roof does not work with the shade of purple on the house. The already-there colour of something permanent like a roof (which is generally not changed for years) needs to be taken into consideration when choosing everything else.
Aside from the roof, pay attention to brick, stone and siding colours.