Ruddy Darter side view

In the process of trying to identify this Darter, which is the most common one in the Netherlands, I learned a few characteristics that separates them:

1) Whether their eyes meet at the top or not
2) Cell structure of their wings
3) Spots and discolorations on their wings
4) Color of their face
5) Width of their abdomen
6) Color of legs and/or any patterns on it

I'm sure there's more attributes, but the key learning for me is that if you spot one, try to photograph it from multiple angles to ease identification.