[iOS] Slider's thumb image doesn't respect color

[kubaflo]

Description

The Slider's thumb image functionality has two issues:

1. It does not respect the ThumbColor property.
2. If a ThumbColor is declared, the thumb image disappears when dragged.

Simulator.Screen.Recording.-.iPhone.16.Pro.Max.-.2025-02-01.at.11.04.22.mp4

Steps to Reproduce

var slider = new Slider() { ThumbColor = Colors.Blue };
Content = new VerticalStackLayout()
{
    slider,
    new Button()
    {
        AutomationId = "ChangeThumbImageButton",
        Text = "Click to change image",
        Command = new Command(() => {
            slider.ThumbImageSource = "coffee.png";
        })
    },
    new Button()
    {
        AutomationId = "ChangeThumbColorButton",
        Text = "Click to change color",
        Command = new Command(() => {
            slider.ThumbColor = Colors.Red;
        })
    }
};

Link to public reproduction project repository

No response

Version with bug

9.0.30 SR3

Is this a regression from previous behavior?

Not sure, did not test other versions

Last version that worked well

Unknown/Other

Affected platforms

iOS

Affected platform versions

No response

Did you find any workaround?

No response

Relevant log output

[similar-issues-ai]

We've found some similar issues:

• Thumb Image Disappears in Slider Control When Changing Thumb Color on iOS and Catalyst #27475 , similarity score: 86%
• [Android, IOS, Mac] Unable to Remove Thumb Image in Slider Control #25939 , similarity score: 81%

If any of the above are duplicates, please consider closing this issue out and adding additional context in the original issue.

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