WP: Modify Visual Editor Toolbar

functions.php

/**
 * Modify TinyMCE4 configurations & Init.
 *
 * @param  array $mceInit config
 * @param  int $editor_id
 * @return array $mceInit
 * @link Modified from https://github.com/mattheu/wp-editor-talk-demo/blob/master/inc/tinymce-mods.php
 */
add_filter( 'tiny_mce_before_init', 'geff_modify_tinyMCE4', 10, 2 );
function geff_modify_tinyMCE4( $mceInit, $editor_id ) {

	// Set the allowed 'Blog formats' - remove h1
	$mceInit['block_formats'] = "Paragraph=p;Header 2=h2;Header 3=h3;Header 4=h4;Header 5=h5;Header 6=h6;Preformatted=pre";

	// We could just set the required buttons on each toolbar if we want.
	// But other plugins may be making modifications so I'm going to and avoid breaking things.

	// Toolbar buttons are stored as a comma separated list - lets make them an array.
	$toolbar1 = explode( ',', $mceInit['toolbar1'] );
	$toolbar2 = explode( ',', $mceInit['toolbar2'] );

	// These are all the buttons we want to completely remove.
	$remove = array(
		'underline',	// underline
		'forecolor'		// text color
	);

	// Remove these buttons if they are found in toolbar1 or toolbar2
	foreach ( $remove as $name ) {

		if ( $key = array_search( $name, $toolbar1 ) ) {
			unset( $toolbar1[$key] );
		}

		if ( $key = array_search( $name, $toolbar2 ) ) {
			unset( $toolbar2[$key] );
		}

	}

	// Convert back to original format.
	$mceInit['toolbar1'] = implode( ',', $toolbar1 );
	$mceInit['toolbar2'] = implode( ',', $toolbar2 );

	return $mceInit;
}