Winter may seem boring and greyish in some areas; I would even say depressive. In Canada, it lasts more than 5 months a year and what about the UK and even Paris, rainy and gray during the long winter months.
Most people will wrap themselves up in a long black coat to go to the office; I agree nothing more professional than black. Although, even if I have a long monochrome coat at home, I sometimes like to swap it for a little punch to illuminate my day. A beautiful colorful coat, can be proudly displayed to meet clients or even on the weekend.
I love this Monaco club piece (from last year). Here are a few coats of different brands of this year that will illuminate your gray days.