Currently, the only way to set the TextColor for the RadNumericInput is to extract the ControlTemplate and set the TextColor of the internal NumericInputEntry component.
A simple and quick fix is to add a TextColor BindableProperty to the RadNumericInput control and use a TemplateBinding on the NumericInputEntry style
It would be nice to be able to change the color of the NumericInput.
Please consider adding 2 bindable property : ButtonBorderColor and ButtonContentColor.
I can't use this control as it is. I had to create my own control.
It should be easy to implement IMHO.