The default white background of your question box can only be changed using custom CSS (Please note that this feature is exclusively available with specific pricing plans). You can remove this background altogether though, no matter which plan you're on.

To remove question backgrounds, go to Theme & Appearance → UI Elements → Questions and toggle off "Questions have background box and shadow"

Selected Answers

The boxes of selected answers (e.g. for Multiple Choice or Product questions) are governed by the Active Color. Both the color and transparency can be customized to whatever you'd like under Active Color in the Theme & Appearance Settings in the Question Panel.

Answer Text

The font color for typed answers matches the Active Color by default. If you would like to change this text to be a different color, you can change it under Theme & Appearance → Typography → Answers.