Okay, that's weird... haven't seen
this one before.
Let's start with the simple ones: Try closing and re-opening the IDE. If that doesn't help, try restarting your computer.
If that still doesn't help, let's first try to find out what could be causing it.
For starters, please check whether the icons in the folder C:\Program Files\GameMaker Studio 2\GUI\Skins\Dark\Images\IDE_Toolbar (default install path - if you changed it, please adapt the path) are also blank white. Note that the icon files are white with a transparent background, so you'll have to select them to see the non-transparent bits if your file explorer's background is also white.
If they're visible here, chances are something is preventing the IDE from loading them. The first thing that comes to my mind here is antivirus or firewall software, so please try temporarily disabling those and then launching GMS 2.
Please let us know if any of this makes any difference.