Our house is like this without the extra roof feature on the front of the garage. The vents will be there in the brick as shown. We have roof vents and soffit vents for circulation in the attic. The sides and back of the house will be cypress green siding. The two end walls are tall with the garage door on one side and a small sliding window on the other. Would it look odd to have the octagonal vents at the gables just for something to break the solid green from the ground to roof. They wouldn't be functional, just decoration. I would like those to be white like the trim. I have looked at houses around here and most of them have the vents to match the siding.

Here is a link that might be useful: house