He is wearing a postal uniform, light blue shirt and gray pants, instead of wearing a postal Jacket, he has a black coat which does not really match the Uniform. The way he is does not really reflect the appearance of a carrier. The expression of his face shows someone who is really tired from the Job who does not have enough time to work and has to get back on duty again. But at the same time, the cleanliness of his uniform shows proudness of having a kind of decent job , as a federal employee with the package of benefits which is included.
The waterproof coat his wearing shows readiness for a cold and rainy day he might be facing, and he holds a pair of gloves to to ensure he will be on top of handling his stuff.
Interesting focus on your work uniform! Uniforms hold a lot of meaning in our culture, as you must know as a veteran. Your semiotic analysis could delve even deeper into the signs on your body that you are able to choose freely–hair, shoes, technology, etc.