How to change the color of searchbar search icon and cancel button color in xamarin forms

As adamm said, you can modify the "cancel button color" via CancelButtonColor.

Similarly, if you want to implement a custom SearchBar in iOS, you can also create a custom renderer for it.

For UISearchBar, you can modify the color of the icon via SearchTextField.LeftView.TintColor.

[assembly: ExportRenderer(typeof(MySearchBar), typeof(MySearchBarRenderer))]
namespace searchbar.iOS
{
    public class MySearchBarRenderer : SearchBarRenderer
    {
        protected override void OnElementChanged(ElementChangedEventArgs<SearchBar> e)
        {
            base.OnElementChanged(e);

            if (Control != null)
            {
                Control.BackgroundColor = UIColor.Yellow;
                UISearchBar searchbar = Control as UISearchBar;
                searchbar.SearchTextField.LeftView.TintColor = UIColor.Orange;
                // UPDATE
                var clearButton = searchbar.SearchTextField.ValueForKey((Foundation.NSString)"clearButton") as UIButton;
                //clearButton.SetTitleColor(UIColor.Blue, UIControlState.Normal);
                //clearButton.TintColor = UIColor.Orange;
                clearButton.SetImage(UIImage.FromBundle("CloseIcon.png"), UIControlState.Normal);
            }
        }
    }
}

Cancel button color can be change by setting CancelButtonColor:

        <SearchBar Placeholder="Search items..."
           CancelButtonColor="Orange"
           PlaceholderColor="Orange"
           TextColor="Orange"
           TextTransform="Lowercase"
           HorizontalTextAlignment="Center"
           FontSize="Medium"
           FontAttributes="Italic" />

For the icon color you need to use custom renderers. For example, on Android you can create a new file (something like SearchBar.Droid.cs) and add this in it:

using Android.Content;
using Android.Widget;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;

[assembly: ExportRenderer(typeof(Xamarin.Forms.SearchBar), typeof(MyApp.Renderers.SearchBarIconColorCustomRenderer))]
namespace MyApp.Renderers
{
    public class SearchBarIconColorCustomRenderer : SearchBarRenderer
    {
        public SearchBarIconColorCustomRenderer(Context context) : base(context) { }

        protected override void OnElementChanged(ElementChangedEventArgs<SearchBar> e)
        {
            base.OnElementChanged(e);
            var icon = Control?.FindViewById(Context.Resources.GetIdentifier("android:id/search_mag_icon", null, null));
            (icon as ImageView)?.SetColorFilter(Color.Orange.ToAndroid());
        }
    }
}

Edit: For iOS, try something like this (I didn't test it):

using UIKit;
using Xamarin.Forms;
using Xamarin.Forms.Platform.iOS;

[assembly: ExportRenderer(typeof(Xamarin.Forms.SearchBar), typeof(MyApp.iOS.Renderers.iOSSearchBarIconColorCustomRenderer))]
namespace MyApp.iOS.Renderers
{
        public class iOSSearchBarIconColorCustomRenderer : SearchBarRenderer
        {
            protected override void OnElementChanged(ElementChangedEventArgs<SearchBar> e)
            {
                base.OnElementChanged(e);
                
                if (Control != null)
                {
                    var searchbar = (UISearchBar)Control;
                    searchbar.TintColor = UIColor.Orange;
                }
            }
        }    
}