Almost any species of wood can be pressure-treated. I don't know what species this post is, though the softer and most abundant pines tend to be used. The little pierce marks you rightly label as telltale indicate that it has been pressure-treated, whether or not it also has been dyed.
The liquid that used to be used contained copper, and gave pressure-treated wood that green copper color. Since the oxidized copper can wear off the surface, color isn't definitive identification. The liquid also contained chromium and arsenic, and thus was called CCA. In the U.S. it's now illegal to use wood treated with CCA in residences. Arsenic and chromium are heavy metals and are toxic or poisonous at low concentrations. I don't know about the other two but arsenic can migrate to soil and from there into plants. That is, it poisons the food you grow. Don't let your vegetable garden even look at that kind of wood!
When it comes to pressure-treated, eco-friendly is a relative concept. The point of pressure treating is to keep out bacteria, fungus, insects, and anything else that might like to eat the wood. So the liquid injected isn't going to be a substance that's friendly to living things. Here's a nice description of some of the alternatives and their relative merits: https://fortress.wa.gov/ecy/publications/publications/0604023.pdf
Short answer: Vegetable gardens and pressure-treated wood are a bad combination. Don't do it.