the server validation errors are not intended to be bold red, only the spry validationsa re.
if you want to change that, edit the webassist/themes/Dark/css/configurable.css file, change:
.textfieldRequiredState .textfieldRequiredMsg, .textfieldInvalidFormatState .textfieldInvalidFormatMsg, .textfieldMinValueState .textfieldMinValueMsg, .textfieldMaxValueState .textfieldMaxValueMsg, .textfieldMinCharsState .textfieldMinCharsMsg, .textfieldMaxCharsState .textfieldMaxCharsMsg, .textareaRequiredState .textareaRequiredMsg, .textareaMinCharsState .textareaMinCharsMsg, .textareaMaxCharsState .textareaMaxCharsMsg, .textfieldServerError, .passwordRequiredState .passwordRequiredMsg, .passwordMinCharsState .passwordMinCharsMsg, .passwordMaxCharsState .passwordMaxCharsMsg, .passwordInvalidStrengthState .passwordInvalidStrengthMsg, .passwordCustomState .passwordCustomMsg, .confirmRequiredState .confirmRequiredMsg, .confirmInvalidState .confirmInvalidMsg, .selectRequiredState .selectRequiredMsg, .selectInvalidState .selectInvalidMsg {
}
to:
.textfieldRequiredState .textfieldRequiredMsg, .textfieldInvalidFormatState .textfieldInvalidFormatMsg, .textfieldMinValueState .textfieldMinValueMsg, .textfieldMaxValueState .textfieldMaxValueMsg, .textfieldMinCharsState .textfieldMinCharsMsg, .textfieldMaxCharsState .textfieldMaxCharsMsg, .textareaRequiredState .textareaRequiredMsg, .textareaMinCharsState .textareaMinCharsMsg, .textareaMaxCharsState .textareaMaxCharsMsg, .textfieldServerError, .passwordRequiredState .passwordRequiredMsg, .passwordMinCharsState .passwordMinCharsMsg, .passwordMaxCharsState .passwordMaxCharsMsg, .passwordInvalidStrengthState .passwordInvalidStrengthMsg, .passwordCustomState .passwordCustomMsg, .confirmRequiredState .confirmRequiredMsg, .confirmInvalidState .confirmInvalidMsg, .selectRequiredState .selectRequiredMsg, .selectInvalidState .selectInvalidMsg {
color:red;
font-weight: bold;
}