Add colors to block editor color palette.

my_custom_colors_block_editor.php

<?php
/**
 * Add colors to block editor color palette.
 * 
 */
function my_custom_colors_block_editor( $editor_settings, $editor_context ) {
	$my_custom_colors = array(
		array(
			'name' => __( 'New Color 1', 'textdomain' ),
			'slug' => 'my-new-color-1',
			'color' => '#BF665E',
		),
		array(
			'name' => __( 'New Color 2', 'textdomain' ),
			'slug' => 'my-new-color-2',
			'color' => '#253659',
		),
		array(
			'name' => __( 'New Color 3', 'textdomain' ),
			'slug' => 'my-new-color-3',
			'color' => '#f2f5f7',
		)
	);
	$editor_settings['colors'] = array_merge( $editor_settings['colors'], $my_custom_colors );
	return $editor_settings;
}
add_filter( 'block_editor_settings_all', 'my_custom_colors_block_editor', 10, 2 );

/**
 * Make sure the palette includes everything from theme.json, your block editor filter, and add more if you want.
 */
function mytheme_setup_theme_supported_features() {
	$editor_settings = get_block_editor_settings( array(), 'core/edit-post' );
	$new_colors = array(
		array(
			'name' => __( 'New Color 4', 'textdomain' ),
			'slug' => 'my-new-color-4',
			'color' => '#03A696',
		),
		array(
			'name' => __( 'New Color 5', 'textdomain' ),
			'slug' => 'my-new-color-5',
			'color' => '#F27457',
		),
	);

	add_theme_support( 'editor-color-palette', array_merge( $editor_settings['colors'], $new_colors ) );
}
add_action( 'after_setup_theme', 'mytheme_setup_theme_supported_features', 11 );