The coordinate-axes.blend shows the coordinate-axes like in viewport, so you can include it in rendering.
It consist of coordinate-axes, CameraTo, x-text, y-text, z-text

All texts are constraint and track to the CameraTo.
All objects are emitter with the colour of the coordinate-axes of the blender-viewport.

You can append the system to your scene selecting the coordinate-axes and the textes by cut/paste (ctrl-c, ctrl-v)
You can move and size the system by moving and sizing the coordinate-axes object.
The size of the texts however has to be adjusted to the sizing of coordinate-axes.

For the texts to show to the camera of your scene you should replace the target "CameraTo" in the constraint to your scene camera.