How to add style to a NumberPicker in Android
<style name="myPicker">
    <item name="android:textColor">#FFFFFF</item>
</style>

np.setValue(10);
np.setMinValue(5);
np.setMaxValue(50);
// retrieve the textview reference
TextView npTextView = (TextView) np.giftAmount.getChildAt(1); // since indexing begins at 0
npTextView.setTextColor(getResources().getColor(
    R.color.my_custom_color)