You choose a shirt for one outfit. You choose a coat for all of them. In cold weather it is the largest colour you wear, and often the only one people see, so test it against the whole wardrobe and not just one favourite outfit.
Each colour below was tested against every outfit in an example wardrobe, using the same model as the wardrobe planner. The best coat depends on what is underneath.
Works over every outfit: black, charcoal, dark brown, dusty rose, mid brown, mid grey, navy, olive, pale blue, tan, deep teal.
Works over every outfit: black, camel, charcoal, dark brown, dusty rose, lavender, light grey, mid brown, mid grey, navy, olive, oxblood, plum, sage, pale blue, tan, deep teal.
Colours here are typical dyed-cloth values, not reference swatches, so navy is the greyed navy of a real suit. Your own garment will differ, and so will the same colour in a different fabric.