Inherit GenerateBlocks buttons from the GeneratePress theme Customizer settings

If you want your GenerateBlock buttons to inherit the color settings in the Customizer (Customize -> Colors -> Buttons), put this in your functions.php.

// Build our CSS.
function tu_gp_gb_button_styling_css() {
	$color_settings = wp_parse_args(
		get_option( 'generate_settings', array() ),
		generate_get_color_defaults()
	);

    return sprintf(
		'.gb-button-wrapper .gb-button, .gb-button-wrapper .gb-button:visited {
			background-color: %1$s;
			color: %2$s;
			padding: 10px 20px;
			border: 0;
			border-radius: 0;
		}

		.gb-button-wrapper .gb-button:hover, .gb-button-wrapper .gb-button:active, .gb-button-wrapper .gb-button:focus {
			background-color: %3$s;
			color: %4$s;
		}',
		$color_settings['form_button_background_color'],
		$color_settings['form_button_text_color'],
		$color_settings['form_button_background_color_hover'],
		$color_settings['form_button_text_color_hover']
	);
}

// Add our CSS to the frontend.
add_action( 'wp_enqueue_scripts', function() {
	wp_add_inline_style( 'generate-style', tu_gp_gb_button_styling_css() );
}, 100 );

// Add our CSS to the editor.
add_filter( 'block_editor_settings_all', function( $settings ) {
	$settings['styles'][] = array( 'css' => tu_gp_gb_button_styling_css() );

	return $settings;
} );

// Remove Button styling from newly added Button blocks.
add_filter( 'generateblocks_default_block_styles', function( $styles ) {
	$styles['button']['backgroundColor'] = '';
	$styles['button']['textColor'] = '';
	$styles['button']['backgroundColorHover'] = '';
	$styles['button']['textColorHover'] = '';
	$styles['button']['paddingTop'] = '';
	$styles['button']['paddingRight'] = '';
	$styles['button']['paddingBottom'] = '';
	$styles['button']['paddingLeft'] = '';

	return $styles;
} );

This will create new CSS that targets GB Button blocks with the GP colors/padding. It will still allow you to design your GB Buttons using the settings if you want.