2018-06-14

Disable High Contrast Mode Windows 10

This is a script we use to disable High Contrast Theme during logon/logoff.
The problem was that some students set High contrast theme, either by choice or by accident and then the settings applied to the lock screen after they logged off, and then the next user got the setting and so on. UEV helped to spread this like a virus in our student computer rooms.

This is the solution!

In your logon and logoff script, run this:

::=== SCRIPT BEGINS ===
:: Set default Theme if High contrast mode is enabled
FOR /f "skip=2 tokens=3 delims= " %%A IN ('REG QUERY "HKEY_CURRENT_USER\Control Panel\Accessibility\HighContrast" /v Flags') do (
SET "reg_value=%%A"
)

IF "%reg_value%" EQU "127" (
C:\Windows\resources\Themes\aero.theme
taskkill /F /IM systemsettings.exe
)
::=== SCRIPT ENDS ===


You can also run this in powershell as a scheduled task running as the logged on user during logon/logoff. But for some reason it did not work every time for me, so I had to go for the logon-script version.


#=== SCRIPT BEGINS ===
# Set this to 1 for visual outputs of variables
$DEBUG = 0
# Set this to SilentlyContinue for no debug, or Continue for debug output
IF ($DEBUG -eq 1) {
    $DebugPreference = "Continue"
} else {
    $DebugPreference = "SilentlyContinue"
    #$DebugPreference = "Continue" # This one is used for debuging debug mode ;)
}

$HighContrastFlags = (Get-ItemProperty 'HKCU:\Control Panel\Accessibility\HighContrast' -Name "Flags").Flags
Write-Debug "`$HighContrastFlags is $HighContrastFlags"

# 127 is High contrast theme, 126 is not high contrast. 
IF ($DEBUG -eq 1) {
    $CheckValue = 126
} Else {
    $CheckValue = 127
}
IF ($HighContrastFlags -eq $CheckValue) {
    Write-Debug "`$HighContrastFlags equals `$CheckValue"
    & $ENV:SYSTEMROOT\resources\Themes\aero.theme
    # Loop ultil file exist or counter is tripped
    $loopCounter = 0
    while (!(Get-Process -ProcessName SystemSettings -ErrorAction Ignore) -and $loopCounter -lt 30) { 
        $loopCounter++
        Start-Sleep 2
        Write-Debug "Loopcounter is $loopCounter"
    }
    Stop-Process -ProcessName SystemSettings -Force
} Else {
    Write-Debug "`$HighContrastFlags does not equal `$CheckValue, script should not run"
}
#=== SCRIPT ENDS ===

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