Those are veins. If they have a pulse, they are arteries. If they dont...they are veins.
This is not the benchmark you want to use for locating veins and differentiating them from arteries. I can feel my pulse of various parts of my body, including certain large veins. It's definitely just untrue that "veins don't have a pulse and arteries do". For an average person, differentiating between veins and arteries should not be difficult. The thing is, it's something that you really want to have someone with a lot of experience demonstrate for you a couple of times.
In general, peripheral veins lie close to the skin, whereas arteries are found deeper. It should not be difficult to avoid arteries if you are injecting into the common areas for new users i.e. the median cubital fossa (the crook of the elbow). There are a lot of large, easy to access veins in this area and it's periphery.
This last paragraph is the most important. If you do hit an artery, there should be no question that you have, as the blood in the arteries is highly pressurized and can even blow the plunger back up the syringe. I can tell you that in over 10 years of intermittent drug injection, I have never touched an artery with a needle. The majority of users I know have never nicked an artery either. It's not a typical experience.
If you would like more specific advice on how to inject properly, feel free to send me a private message, but there are actually a lot of great resources for this purpose all over the net. The problem is, it's like trying to tell someone how to throw a good fastball with nothing but text instructions. If you have a professional pitcher stop by and literally place your fingers on the seems a couple of times, you'll be set to throw fastballs for the rest of your life.
It's a tricky thing to teach in this manner, but I can tell you that there is a great deal of different between hitting a vein and hitting an artery.