It may look gray depending on the light, but I think it is dark blue. This jacket seems to be sold only in indigo. I think it is dyed with a color that contains blue because it becomes blue when you increase the sensitivity of the image.
When the light changes, it may turn grey, but it appears to be dark blue. The jacket appears to be sold only in indigo. When the intensity of the image was increased, it turned blue, so it may have been dyed in a colour that contains blue.