How to use the Theme function? (Not the Theme function at Rayfield:CreateWindow)

[deedlemcdoodledeedlemcdoodle-creator]

How to actually use Window.ModifyTheme('ThemeIdentifier')?

I want to make a Color Theme Changer using a Dropdown and a Button, here's 2 concepts:

↓Dropdown
Default
Amber Glow
Amethyst
Bloom
Dark Blue
Green
Light
Ocean
Serenity

Button: "Change Color Theme"

And

Button:

Default
Amber Glow
Amethyst
Bloom
Dark Blue
Green
Light
Ocean
Serenity

All of them are clickable to change Color Themes.

I tried coding to make them work but it didn't work, please help.