Make any window transparent using PowerShell. Modified from https://gist.github.com/grenade/ed8dd77ae8eeb5b4a3c1cfd66e9c8ae7

Set-Transparency.ps1

$user32 = Add-Type -Name 'user32' -Namespace 'Win32' -PassThru -MemberDefinition @'
  
  [DllImport("user32.dll")]
  public static extern int GetWindowLong(IntPtr hWnd, int nIndex);
  
  [DllImport("user32.dll")]
  public static extern int SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong);
  
  [DllImport("user32.dll", SetLastError = true)]
  public static extern bool SetLayeredWindowAttributes(IntPtr hWnd, uint crKey, int bAlpha, uint dwFlags);
'@

<#
.SYNOPSIS
    This function can be used to change the transparency of any window provided it has a mainwindowhandle on the process.
.PARAMETER Process
    Process name you would like to modify transparency on.
.PARAMETER Transparency
    This is a number between 0 and 255. 0 is completely transparent and 255 is completely opaque.
.EXAMPLE
    C:\PS> Get-Process winword.exe | % { Set-Transparency -Process $_ -Transparency 128 }
#>
function Set-Transparency {
    param([string]$Process, [int]$transparency = 200)

    Get-Process $Process | ? { $_.MainWindowHandle -ne 0 } | ForEach-Object {
        $wl = $user32::GetWindowLong($_.MainWindowHandle, -20)
        $user32::SetWindowLong($_.MainWindowHandle, -20, ($wl -bor 0x80000)) | Out-Null
        $user32::SetLayeredWindowAttributes($_.MainWindowHandle, 0, $transparency, 0x02) | Out-Null
    }

}