Custom color palette

In TinyMCE I used to add a custom color palette function to my functions.php file so I could restrict the color options available to editors. Here was my code:

function my_mce4_options( $init ) {
$default_colours = '
"103A5C", "Dark Blue",
"144C93", "Med Blue",
"CEE7FF", "Light Blue",
"68AAF2", "Bright Blue"
"222222", "Almost Black",
"444444", "Slate Gray",
"666666", "Charcoal",
"e6e6e6", "Light Gray",
"cacaca", "Medium Gray",
"fefefe", "Almost White",
"ffffff", "White"
';
$init['textcolor_map'] = '['.$default_colours.']';
$init['textcolor_rows'] = 2;
$init['textcolor_cols'] = 6;

return $init;
}
add_filter('tiny_mce_before_init', 'my_mce4_options');

This code now causes problems with the Classic Editor plugin and Advanced Editor Tools. I get the white text on white background in the visual editor window, and no buttons. After much debugging I discovered that this code is the culprit.

So my question is how can I accomplish this now?