GMod starts up and is nothing but blue

It’s not a BSOD but my GMOD window is blue.

I can hear the mouse hover over the menu and stuff…but can’t see through blue.

Er… overlay error? Try running in fullscreen. Right-click on your GMod in Steam Games. Go to Properties. Click on Set Launch Options. Type in -fullscreen

If that doesnt work reinstall.

if that doesnt work its your computer,and what OS are you using.