The title "WPF Label Foreground Color" is very simple (exactly what I was looking for) but the OP's code is so cluttered it's easy to miss how simple it can be to set text foreground color on two different labels:
<StackPanel>
<Label Foreground="Red">Red text</Label>
<Label Foreground="Blue">Blue text</Label>
</StackPanel>
In summary, No, there was nothing wrong with your snippet.