the foreground property does not apply to the icon .. He has followed these steps:
https://docs.telerik.com/windows-universal/controls/raddatepicker-and-radtimepicker/styling/raddatetimepickers-explicitstyling
and it only takes the color indicated by the text and not the icon ..
This is my XAML code:
<Custom:RadDatePicker x:Name="FromDatePicker" HorizontalAlignment="Left" ValueChanged="DatePickerValueChange">
<Custom:RadDatePicker.Resources>
<Style TargetType="Custom:RadDatePicker">
<Setter Property="Foreground" Value="Orange"/>
<Setter Property="FontSize" Value="15"/>
<Setter Property="FontStyle" Value="Italic"/>
<Setter Property="Background" Value="Beige"/>
<Setter Property="BorderBrush" Value="Orange"/>
</Style>
</Custom:RadDatePicker.Resources>
</Custom:RadDatePicker>
the result is in the attached image ..