While in LT, go to the Tools pulldown menu, select
Options, on the pop-up that appears select the
Display tab, in the
Window Elements section
click on the
Colors button, select Modelspace, select Background color (older versions only gie you the one choice), select color, then your choice.
Notice that you can change other colors of other display entities and areas there, spend a little time and adjust all items to meet your visual needs.