why my Custom theme is not working in angular?

I want to create a custom theme in angular. here is my code in style.scss file

@use '@angular/material' as mat;

@include mat.core();
// Define a light theme
$app-light-primary: mat.define-palette(mat.$indigo-palette, 900);
$app-light-accent: mat.define-palette(mat.$green-palette);

$app-light-theme: mat.define-light-theme((color: (primary: $app-light-primary,
                accent: $app-light-accent,
            )));

// Define a dark theme
$app-dark-primary: mat.define-palette(mat.$teal-palette, 900);
$app-dark-accent: mat.define-palette(mat.$lime-palette);
$app-dark-theme: mat.define-dark-theme((color: (primary: $app-dark-primary,
                accent: $app-dark-accent,
            )));

// Apply the light theme by default
@include mat.all-component-themes($app-light-theme);

// Apply the dark theme only when the `.dark-theme-mode` CSS class is applied
// to an ancestor element of the components (such as `body`).
.dark-theme-mode {
    @include mat.all-component-themes($app-dark-theme);
}

My light theme color palate is not working. it is by default indigo. I want to use indigo, 900. can anybody help?