You can change the grid line color by going to Edit ---> Preferences ---> Colors and then changing the Grid color.
For the background color, the grid does not have a background color. What you see is the default skybox image.
Windows ---> Lightning ---> Settings then go to Scene tab and remove the Skybox Material. Set it to "None". You can also create new material then use "Skybox/Procedural" as your material.
You can change the grid line color by going to Edit ---> Preferences ---> Colors and then changing the Grid color.
For the background color, the grid does not have a background color. What you see is the default skybox image.
Windows ---> Lightning ---> Settings then go to Scene tab and remove the Skybox Material. Set it to "None". You can also create new material then use "Skybox/Procedural" as your material.