Description
You open the 3D window, change the sky or background color in your current 3D Style, but the 3D model still shows the same physically based sky dome with no visible change in the sky color, the background looks like an atmospheric sky instead of a flat solid color.
Solution
This happens when Physically based rendering in 3D Window is enabled in the Work Environment, which overrides the standard 3D style sky background settings and uses a procedural sky instead.
You must first turn off the physically based renderer in Work Environment, then adjust the 3D background using 3D Styles or s as needed.
Turn off physically based rendering in Work Environment
Go to Options > Work Environment > More Options.
In the More Options dialog expand the Experimental Features tab.
Clear the checkbox named Enable Physically Based Rendering in 3D to disable this setting in the 3D window.
Click OK to close the dialog and apply the change.
Note: After you disable this experimental feature, the 3D window returns to the default hardware or vector 3D engine defined by your active 3D Style, and background color controls become effective again.
Check and adjust the active 3D Style background
With the 3D window active, open View > 3D View Options > 3D Styles to edit the active style.
Select the 3D Style used by your current 3D view from the list on the left side of the dialog.
In the Background section, choose one of the available options:
Sky Color / Ground Color and set the desired sky color.
As in PhotoRendering to inherit a sky setup from PhotoRendering.
Click the sky color field and pick your preferred sky color from the color chooser.
Click OK to save the 3D Style and return to the 3D window.
Note: If you save a View of this 3D window, it will keep the chosen 3D Style and sky color, so opening the View in the future will display the same background consistently.