IMenuItem disabled color change.

DroidExtensions.cs

public static class DroidExtensions
{
	public static IMenuItem SetEnabled(this IMenuItem item, bool enabled, Context context, int iconId)
	{
		return item.SetEnabled(enabled, context, iconId, Color.Gray);
	}

	public static IMenuItem SetEnabled(this IMenuItem item, bool enabled, Context context, int iconId, Color disabledColor)
	{
		var resIcon = context.Resources.GetDrawable(iconId);

		if (!enabled)
			resIcon.Mutate().SetColorFilter(disabledColor, PorterDuff.Mode.SrcIn);

		item.SetEnabled(enabled);
		item.SetIcon(resIcon);
		
		return item;
	}
}