Here is a simple little code drop that will allow you to customize the colors that you find in the WordPress post editor’s font color. You can add however many colors that you wish here. Note: I’ve removed the default colors completely because I simply do not need them.

This is a great resource if you are building a website for a client with a specific color scheme and would like an easy way for them to change text colors while writing a post (or page).

// change buttons in WYSWIG post editor, edit color palette
function art_mce4_options( $init ) {
$custom_colours = '
"5fc5be", "artifakt Light Blue",
"293d70", "artifakt Dark Blue",
"576c88", "artifakt Light Grey",
"373737", "artifakt Dark Grey",
$init['textcolor_map'] = '['.$custom_colours.']';
$init['textcolor_rows'] = 1; // decrease to 1 row
return $init;
add_filter('tiny_mce_before_init', 'art_mce4_options');

Simply put the above code in your functions.php file and you are off to the races!