Wordpress editor showing white text

Check your javascript console. If you see an error like:

"post.php?post=2840&action=edit:2783 Uncaught ReferenceError: tinymce is not defined"

Then the loading of wp-tinymce.php failing. Because the editor hasn't loaded, it appear as if your text is white, or "invisible" in the editor. This can be worked-around by adding:

define('CONCATENATE_SCRIPTS', false);

(Per Tijmen above, or https://wordpress.stackexchange.com/a/63172/118510)

(I use WP Fastest Cache plugin which has it's own concatenation, so if I use that plugin, then I'm OK skipping the default Wordpress concatenation.)

The root problem, however, is that a request to:

/wp-includes/js/tinymce/wp-tinymce.php?c=1&ver=4506-20170408

Is failing or receiving a 404. This could be due to a security restriction on your hosting or CDN.

Let's start with the obvious: is your Wordpress install completely up-to-date, including all plug-ins, themes etc?

It could help to actively declare the color to be black, instead of simply removing the line of CSS you removed, so:

.js .tmce-active .wp-editor-area{color:#000000} 

Alternatively, this issue has been known to be caused by several plugins, such as PS Disable Autoformatting, however that instance was a few years ago. Did you recently install a plug-in? If so, try disabling that plug-in to see if that returns the editor to normal.

If none of this solves the issue, you can also try downloading Wordpress and replacing the /wp-includes/js/tinymce/ folder. Although it's unlikely, it's not impossible that something went wrong during an update or so.

If nothing else works, according to this link, you can open your wp-config.php file and add the following line at the very top after the php opening tag.

define('CONCATENATE_SCRIPTS', false);

I have just fixed this problem and thought it would be worth mentioning this basic check to others. If you are installing another theme or a second theme that installs it's own set of plugins, make sure you don't have any existing plugin composers installed or still activated. This can cause the conflict that makes the text white and the tabs to not work.

For me, I had both CMSMasters Content Composer (From previous theme) and WPBakery Visual Composer (From new theme) installed and active, which gave me this exact issue. I had also tried replacing the tinymce file and adding the extra line to wp-config, but none of these worked. Deactivating CMSMasters Content Composer fixed the white text issue for me.