Change color of validation error on NetTier

To change color of auto generated validation error please use the following procedure. Here I'll take example of EntityDropdownlist required Validator.

Look for the page {ProjectName}.Web\UI\EntityDropDownList.cs

  // Required field?
            if ( Required && !ReadOnly )
            {
                requiredValidator.Enabled = false;
                requiredValidator.ControlToValidate = this.ID;
                requiredValidator.ID = this.ID + "_RQ";
                requiredValidator.Text = ErrorText;
                requiredValidator.ErrorMessage = RequiredErrorMessage;
                requiredValidator.ForeColor = Color.Red;
                requiredValidator.EnableClientScript = EnableClientScript;
requiredValidator.ValidationGroup = this.ValidationGroup;
                this.Controls.Add( requiredValidator );
            }

And you are good to go.