[NSFW] The color of the text being entered into the form

That is a theme issue. Try switching theme to the default one.

Why you are advised to deactivate plugins and switch to the default theme.

Thank you for the answer!

While the issue is of the theme or another plugin overriding CSS the issue can easily be resolved with the following custom style

.wpcf7-form-control-wrap textarea {
color: #666666;
}

This will make the text area font the same as your other form elements.

If on the off chance that does not work try

.wpcf7-form-control-wrap textarea {
color: #666666 !important;
}