GUACAMOLE-630: Preserve raw contents of color scheme if manually edited.

guacamole/src/main/webapp/app/form/controllers/terminalColorSchemeFieldController.js

@@ -77,14 +77,12 @@ angular.module('form').controller('terminalColorSchemeFieldController', ['$scope
     // Keep selected color scheme and custom color scheme in sync with changes
     // to model
     $scope.$watch('model', function modelChanged(model) {
-        if (!model)
-            $scope.selectedColorScheme = '';
-        else if (_.includes($scope.field.options, model))
-            $scope.selectedColorScheme = model;
-        else {
+        if ($scope.selectedColorScheme === CUSTOM_COLOR_SCHEME || (model && !_.includes($scope.field.options, model))) {
             $scope.customColorScheme = ColorScheme.fromString(model);
             $scope.selectedColorScheme = CUSTOM_COLOR_SCHEME;
         }
+        else
+            $scope.selectedColorScheme = model || '';
     });
 
     // Keep model in sync with changes to selected color scheme

guacamole/src/main/webapp/app/form/types/ColorScheme.js

@@ -242,7 +242,7 @@ angular.module('form').factory('ColorScheme', [function defineColorScheme() {
     ColorScheme.toString = function toString(scheme) {
 
         // Use originally-provided string if it equates to the exact same color scheme
-        if (scheme._originalString && ColorScheme.equals(scheme, ColorScheme.fromString(scheme._originalString)))
+        if (!_.isUndefined(scheme._originalString) && ColorScheme.equals(scheme, ColorScheme.fromString(scheme._originalString)))
             return scheme._originalString;
 
         // Add background and foreground