Yellowish? It could be that the light colour or enviroment light colour, is defaulting to a yellowish colour. So you might have to change the colour to a colour that you want for your scene.
If you want try this test. Change the colour in your light settings, to a weird colour like red, and see what happens. If the colours in the entire scene change reddish, and the yellow colour completely disappears, then that is a sign that the yellow problem, is due to the colour of the light or enviroment light emission. So you might have to change the colour in your settings, to a colour that might look good in your scene.
In addition the environment lighting in your render settings. Also look at the default directional light that Unity creates when you create a new, empty scene. That’s yellowish too, if I recall.
Ok, fixed it thank god!
I launched a scene that came with one of the assets I downloaded from the Asset Store (which was fine, with no yellowish atmosphere), and when I got back to my scene, the yellowish atmosphere disappeared