A slate blue shift dress is appropriately dark and composed without reading as stark. The straight cut moves with you without demanding attention. Shift dresses work best in substantial fabrics that hold their structure through wearing and through the emotional weight of the day. Slate blue is dark enough to be respectful and warm enough to not feel cold or severe. A midi length feels appropriate and works through services and receptions without shifting or riding up. Long sleeves are respectful and the simple neckline keeps the focus on the fact that you are present and composed. Pair with dark shoes and minimal jewelry. The total effect is grounded and dignified without requiring any visible effort.