Blender Painting and unwraping multiple objects

Hello, i tried to look after this everywhere, unfortunately, i dont even know how to name this issue. I am trying to make a Railway, and i had something, but i deleted all because i Cant figure out how to hand paint it when it is done. As you see on the image, only one object is Paintable, i cant duplicate it, ale copy paste, i jsut dont know how to do this. So i want to paint both of those objects, but how to make them paintable (purple) ?

Hey George,

Welcome to the forum!
The purple color indicates that there is no texture yet. You’ll need to create one.
It’s good that you’ve started by using the Texture Paint environment by clicking on that tab.
In the UV window, you’ll not there is a “+New” button. This creates a fresh texture you can paint on.

I don’t know if it will help, but here are a couple of one-minute videos about texture painting.

I’m afraid these are for 2.79, so maybe some things are no longer up-to-date. I will update them at a future date.