Mailjet ticket support system boils down to either

1) write about this issue in our feedback forum or
2) we don't have plans to implement this, maybe later who knows

And we are talking about basic functionality. I get the impression they don't care about their customers.

We need the ability to change the text colour of the success and error message. I am using a form with a blue background and the success message is in grey so it is not visible against the dark blue.
Mailjet has given us the ability to design our own forms, yet part of that process is not working if my subscribers are unable to read success or error messages because the text colour can't be changed. Please allow users to change the colour of the success and error message text.
I wouldn't class this as a suggestion - this is a functionality error that should be put on the list to fix. I raised a support ticket but they suggested I request it instead of just fixing it?

Newsletter - widget:
Leider ist die Funktionalitaet, die Nachricht nach klick auf "anmelden" im Newsletter-widget frei zu gestalten auch wenige tage vor auslaufen der alten Widgets noch nicht implementiert. Es waere schoen, wenn dabei die Nachricht frei gestaltet werden koennte, im Idealfall aehnlich der Widgetgestaltung an sich.

Message after click on newsletter widget: send
Newsletter widget:
Unfortunately, the functionality to freely design the message after clicking on "subscribe" in the newsletter widget is not yet implemented even a few days before the old widgets expire. It would be nice if the message could be designed freely, ideally similar to the widget design itself.