This is a great jacket. Warm and cozy. The indigo is a true indigo - slightly more purple than navy. I waffled on the size because the reviews don't say much about that. I am 5'4, 140 lbs and the size small was perfect for me. I am from Canada, so I wanted to be able to layer warmer sweaters underneath. If you plan on only wearing a T-Shirt, an xs would probably be ok. As a note - Canadian duties and fees were over $70, so keep that in mind - not Derby's fault, just the Canadian tax system on goods arriving here.
