Sometimes the Active Color you choose works well for question selections but not for text answers. For example, yellow might work well for a Multiple Choice selection, but not be legible when your respondent is typing text into an Address field.
To change the font color of typed answers only, head to Theme → Typography → Answers.
Typed answers will match the Active Color (in the Theme Settings menu) unless it is changed separately here in the Typography menu.
For finer control over colors of different answers, you would need to use Custom CSS, which is only exclusively available with specific pricing plans.
Gotchas
If your Active Color simply isn't standing out enough, try choosing a darker Background Color instead to increase the overall contrast. You can also remove the white background on individual questions.
The font and color of Dropdown answers are also be affected by the Answers settings in the Typography menu, even though these are usually selected rather than typed.