List of all colors available for PowerShell?

The console colors are in an enum called [System.ConsoleColor]. You can list all the values using the GetValues static method of [Enum]

[Enum]::GetValues([System.ConsoleColor])

or just

[Enum]::GetValues([ConsoleColor])

Pretty grid

$colors = [enum]::GetValues([System.ConsoleColor])
Foreach ($bgcolor in $colors){
    Foreach ($fgcolor in $colors) { Write-Host "$fgcolor|"  -ForegroundColor $fgcolor -BackgroundColor $bgcolor -NoNewLine }
    Write-Host " on $bgcolor"
}

Updated colours in newer powershell:

https://gist.github.com/timabell/cc9ca76964b59b2a54e91bda3665499e