Managing accessibility settings across a large Windows 10 deployment presents unique challenges. While high contrast mode serves legitimate accessibility needs, accidental activation creates unnecessary helpdesk tickets. The standard toggle (Alt+Shift+Print Screen) becomes impractical at scale, and complete lockdown of accessibility settings isn't viable when some users genuinely require these features.

The high contrast setting stores its state in the Windows Registry. Here's the key location:

HKEY_CURRENT_USER\Control Panel\Accessibility\HighContrast

A PowerShell script can modify this setting system-wide:

# Disable High Contrast Mode via PowerShell
Set-ItemProperty -Path "HKCU:\Control Panel\Accessibility\HighContrast" -Name "Flags" -Value 0
Stop-Process -Name explorer -Force  # Restart explorer to apply changes

For enterprise deployment, consider these GPO approaches:

1. Create a Computer Configuration preference:
   - Path: User Configuration → Preferences → Windows Settings → Registry
   - Action: Replace
   - Hive: HKEY_CURRENT_USER
   - Key Path: Control Panel\Accessibility\HighContrast
   - Value name: Flags
   - Value type: REG_DWORD
   - Value data: 0

2. Deploy via Startup Script:
   reg add "HKCU\Control Panel\Accessibility\HighContrast" /v Flags /t REG_DWORD /d 0 /f

For environments with mixed accessibility needs:

<# Conditional deployment script example #>
$needsAccessibility = Get-ADUser -Filter * -Properties ExtensionAttribute1 | 
    Where-Object {$_.ExtensionAttribute1 -eq "AccessibilityRequired"}

if (-not $needsAccessibility) {
    Set-ItemProperty -Path "HKCU:\Control Panel\Accessibility\HighContrast" -Name "Flags" -Value 0
}

To maintain settings between sessions:

# Scheduled Task to check high contrast state hourly
$action = New-ScheduledTaskAction -Execute 'PowerShell.exe' -Argument '-NoProfile -WindowStyle Hidden -Command "if ((Get-ItemProperty -Path \"HKCU:\Control Panel\Accessibility\HighContrast\").Flags -ne 0) { Set-ItemProperty -Path \"HKCU:\Control Panel\Accessibility\HighContrast\" -Name \"Flags\" -Value 0; Stop-Process -Name explorer -Force }"'
$trigger = New-ScheduledTaskTrigger -Once -At (Get-Date) -RepetitionInterval (New-TimeSpan -Hours 1)
Register-ScheduledTask -TaskName "HighContrastMonitor" -Action $action -Trigger $trigger -RunLevel Highest

For scenarios requiring GUI interaction:

Add-Type -AssemblyName UIAutomationClient
$condition = New-Object System.Windows.Automation.PropertyCondition(
    [System.Windows.Automation.AutomationElement]::NameProperty,
    "Turn off high contrast"
)
$element = [System.Windows.Automation.AutomationElement]::RootElement.FindFirst(
    [System.Windows.Automation.TreeScope]::Descendants,
    $condition
)
if ($element) {
    $pattern = $element.GetCurrentPattern([System.Windows.Automation.InvokePattern]::Pattern)
    $pattern.Invoke()
}

In enterprise Windows 10 environments, we frequently encounter users accidentally enabling high contrast themes through the keyboard shortcut (Left Alt+Left Shift+Print Screen) or accessibility settings. While this feature serves legitimate accessibility needs, unauthorized activation creates unnecessary helpdesk tickets and user confusion.

The most reliable method involves modifying the following registry keys:

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Control Panel\Accessibility\HighContrast]
"Flags"="126"
"High Contrast Scheme"=""
"High Contrast Scheme Size"=dword:00000000

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Themes]
"LastHighContrastTheme"=""
"HighContrast"="no"

For automated deployment, use this PowerShell script that handles both current user and default user configurations:

function Disable-HighContrast {
    param (
        [switch]$AllUsers
    )
    
    if ($AllUsers) {
        $regPath = "Registry::HKEY_USERS\.DEFAULT\Control Panel\Accessibility\HighContrast"
        Set-ItemProperty -Path $regPath -Name "Flags" -Value "126" -ErrorAction SilentlyContinue
        Set-ItemProperty -Path $regPath -Name "High Contrast Scheme" -Value "" -ErrorAction SilentlyContinue
    }
    else {
        $regPath = "HKCU:\Control Panel\Accessibility\HighContrast"
        Set-ItemProperty -Path $regPath -Name "Flags" -Value "126"
        Set-ItemProperty -Path $regPath -Name "High Contrast Scheme" -Value ""
        
        $themePath = "HKCU:\Software\Microsoft\Windows\CurrentVersion\Themes"
        Set-ItemProperty -Path $themePath -Name "LastHighContrastTheme" -Value ""
        Set-ItemProperty -Path $themePath -Name "HighContrast" -Value "no"
    }
    
    # Refresh the active session
    $signature = @'
    [DllImport("user32.dll", CharSet=CharSet.Auto)]
    public static extern int SystemParametersInfo(int uAction, int uParam, string lpvParam, int fuWinIni);
'@
    $SPI_SETNONCLIENTMETRICS = 0x002A
    $SPIF_UPDATEINIFILE = 0x01
    $SPIF_SENDCHANGE = 0x02
    $winAPI = Add-Type -MemberDefinition $signature -Name WinAPI -Namespace SystemParams -PassThru
    $winAPI::SystemParametersInfo($SPI_SETNONCLIENTMETRICS, 0, $null, $SPIF_UPDATEINIFILE -bor $SPIF_SENDCHANGE) | Out-Null
}

# Usage examples:
Disable-HighContrast  # For current user
Disable-HighContrast -AllUsers  # For default user profile

For domain environments, create a Group Policy Preference (GPP) to deploy the registry changes:

1. Create a new GPO and navigate to: User Configuration > Preferences > Windows Settings > Registry
2. Add the following registry items:
   • Action: Update
     Hive: HKEY_CURRENT_USER
     Key Path: Control Panel\Accessibility\HighContrast
     Value name: Flags
     Value type: REG_SZ
     Value data: 126
   • Repeat for other values mentioned in the registry solution
3. Set the GPP to apply once and not reapply

For environments without GPO access, implement this WMI-based solution that triggers on user logon:

$trigger = New-JobTrigger -AtLogOn -RandomDelay 00:00:30
$options = New-ScheduledJobOption -RunElevated
Register-ScheduledJob -Name "DisableHighContrast" -ScriptBlock {
    $current = Get-ItemProperty -Path "HKCU:\Control Panel\Accessibility\HighContrast" -Name "Flags" -ErrorAction SilentlyContinue
    if ($current -and $current.Flags -ne "126") {
        Disable-HighContrast
    }
} -Trigger $trigger -ScheduledJobOption $options

• Always test in a non-production environment first
• Document the changes for accessibility compliance
• Consider creating an approved high-contrast theme for users with visual impairments
• The registry changes may require a logoff/logon to take full effect