What you’re describing is “mist”…
First, go into EDIT(F9) panels, and hit show “limits” on the camera.
This gives you visualisation of the a line showing clipping distance range (how far the camera can see), which are changed in Clipping “start” and “end” in same panel. There is a DoF (Depth of Focus) attribute which is useful of you can use nodes and want to make blurry in-and-out-of focus effects.
…but these don’t actually change the mist values. To find these, go into the world settings, under SHADING(F5) and then the far right “world” icon. You should see a button to enable “mist”, which then has “start” for how far away from camera things begin to fade, and then “distance” for how long before the image is completely misted out.
Mist fades to become your environment / world colour.
Hope that was clear enough. Settings are kind of in two places. Attached example to play with.
mist.blend (45.1 KB)