in the webassist/forms/fd_sharp_default.css file, the following style is setting the color for the failed text area to white:
form.Sharp_Default textarea.textareaRequiredState, form.Sharp_Default .textareaRequiredState textarea, form.Sharp_Default textarea.textareaMinCharsState, form.Sharp_Default .textareaMinCharsState textarea, form.Sharp_Default textarea.textareaMaxCharsState, form.Sharp_Default .textareaMaxCharsState textarea {
background-color: #B40000;
border-color: #8C8C8C;
color: #FFFFFF;
}
you can change that to black by changing the css to:
form.Sharp_Default textarea.textareaRequiredState, form.Sharp_Default .textareaRequiredState textarea, form.Sharp_Default textarea.textareaMinCharsState, form.Sharp_Default .textareaMinCharsState textarea, form.Sharp_Default textarea.textareaMaxCharsState, form.Sharp_Default .textareaMaxCharsState textarea {
background-color: #B40000;
border-color: #8C8C8C;
color: #000000;
}