Tkx and configure

Hello,

I want to change the appearance of a Tkx widget, but it behaves
different than expected:

my $frame = $mw->new_ttk__labelframe(
        -text        => "test",
        -labelanchor => 'nw',
    );
$frame->configure(-text => "TEST"); #works
$frame->configure(-foreground => "red"); #does NOT work, -foreground not recognised

How do I change colors in Tkx?

Thank you.