E-mail Validator Widget: How to change text colour of message

I wonder how it's possible to change the text after email verification, the "message about sending code". In the widget properties of the e-mail validator you can change the text "message about sending code". But how can I change the colour from black into white?

In my form the message text I want to change in colour ist the following:

"Dein Verifizierungs Code wurde dir per Mail gesendet an  {mail}.

Überprüfe deine Mailbox und füge den gesendeten Code im Feld ein, um die Verifizierung abzuschliessen."

You can use the HTML tag font color in the Message about sending code box.

<font color="white">Text here</font>

Here's an example:

Here's the result:

Let us know if you have any questions. Thank you.

Thank you very much Jan, that's very helpful. Now the text goes beyond the dark background. Can you help me narrow the text on the right side? 

The widget overflows the form container due to its size.

You may reduce the widget's width, or change the label alignment to the Top.