processredirect2.ps1

& {
    [CmdletBinding()]
    param()

    $psi = [Diagnostics.ProcessStartInfo]@{
        UseShellExecute        = $false
        RedirectStandardError  = $true
        RedirectStandardOutput = $true
        FileName               = 'cmd.exe'
        Arguments              = '/c "ping -n 10 google.com & echo an error >&2"'
    }
    $proc = [Diagnostics.Process]@{
        StartInfo = $psi
    }

    $params = @{
        InputObject      = $proc
        EventName        = 'OutputDataReceived'
        SourceIdentifier = 'Process.Stdout'
        Action           = {
            $cmdlet.WriteObject("$([char] 27)[32mSTDOUT:$([char] 27)[0m " + $EventArgs.Data)
        }
    }
    $sub = Register-ObjectEvent @params
    $sub.Module.SessionState.PSVariable.Set('cmdlet', $PSCmdlet)

    $params['EventName']        = 'ErrorDataReceived'
    $params['SourceIdentifier'] = 'Process.Stderr'
    $params['Action']           = {
        $cmdlet.WriteObject("$([char] 27)[91mSTDERR:$([char] 27)[0m " + $EventArgs.Data)
    }
    $sub = Register-ObjectEvent @params
    $sub.Module.SessionState.PSVariable.Set('cmdlet', $PSCmdlet)

    Register-ObjectEvent -InputObject $proc -EventName Exited -SourceIdentifier Process.Exited

    try {
        $proc.Start() | Out-Null
        $proc.BeginOutputReadLine()
        $proc.BeginErrorReadLine()

        Wait-Event -SourceIdentifier Process.Exited | Remove-Event
    }
    finally {
        Unregister-Event -SourceIdentifier Process.Stdout
        Unregister-Event -SourceIdentifier Process.Stderr
        Unregister-Event -SourceIdentifier Process.Exited
    }
}