I’m trying to make a design where the text is the opposite color as the color behind it, but I don’t know how to do that. How can I achieve this effect?
The blend mode is called “Difference” (or Negation which GD don´t have)
which probably do what you want. Unfortunately I can´t confirm this in Gravit Designer - maybe that´s because I don´t have the Pro version (which I can´t afford.)