reply to Draiman
Re: Garage addition That depends whether you want the columns to blend in with the garage or whether you want to make them stand out (to make them more noticeable to the drivers in your household). Some might like them to be a different color for aesthetic or practical reasons.
Assuming you are using an appropriate primer I don't see any reason why you couldn't use the same top coat. The nice thing about using the same paint is that you don't need to worry about drips while painting the columns.
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