diff --git a/main-window.c b/main-window.c
index 600bf0a..e25ebdb 100644
--- a/main-window.c
+++ b/main-window.c
@@ -114,7 +114,6 @@ static void on_load_gds(gpointer button, gpointer user)
 	char *filename;
 	GString *mod_date;
 	GString *acc_date;
-	GdkRGBA cell_text_color;
 
 	open_dialog = gtk_file_chooser_dialog_new("Open GDSII File", ptr->main_window, GTK_FILE_CHOOSER_ACTION_OPEN,
 						  "Cancel", GTK_RESPONSE_CANCEL, "Open GDSII", GTK_RESPONSE_ACCEPT, NULL);
@@ -175,11 +174,6 @@ static void on_load_gds(gpointer button, gpointer user)
 				mod_date = generate_string_from_date(&gds_c->mod_time);
 				acc_date = generate_string_from_date(&gds_c->access_time);
 
-				cell_text_color.alpha = 1;
-				cell_text_color.red = (double)61.0/(double)255.0;
-				cell_text_color.green = (double)152.0/(double)255.0;
-				cell_text_color.blue = 0.0;
-
 				/* Add cell to tree store model
 				 * CELL_SEL_CELL_COLOR will always be green,
 				 * because no cell cehcker is implemented, yet.
@@ -188,7 +182,7 @@ static void on_load_gds(gpointer button, gpointer user)
 						    CELL_SEL_CELL, gds_c,
 						    CELL_SEL_MODDATE, mod_date->str,
 						    CELL_SEL_ACCESSDATE, acc_date->str,
-						    CELL_SEL_CELL_COLOR, &cell_text_color, // TODO: implement cell checker
+						    CELL_SEL_CELL_ERROR_STATE, 0, // TODO: implement cell checker
 						    -1);
 
 				/* Delete GStrings including string data. */
diff --git a/tree-renderer/lib-cell-renderer.c b/tree-renderer/lib-cell-renderer.c
index 192210b..c5fe6c9 100644
--- a/tree-renderer/lib-cell-renderer.c
+++ b/tree-renderer/lib-cell-renderer.c
@@ -25,6 +25,7 @@ G_DEFINE_TYPE(LibCellRenderer, lib_cell_renderer, GTK_TYPE_CELL_RENDERER_TEXT)
 enum {
 	PROP_LIB = 1,
 	PROP_CELL,
+	PROP_ERROR_LEVEL,
 	PROP_COUNT
 };
 
@@ -38,24 +39,56 @@ static void lib_cell_renderer_constructed(GObject *obj)
 	G_OBJECT_CLASS(lib_cell_renderer_parent_class)->constructed(obj);
 }
 
+static void convert_error_level_to_color(GdkRGBA *color, unsigned int error_level)
+{
+
+	/* Always use no transparency */
+	color->alpha = 1.0;
+
+	if (error_level & LIB_CELL_RENDERER_ERROR_ERR) {
+		/* Error set. Color cell red */
+		color->red = 1.0;
+		color->blue = 0.0;
+		color->green = 0.0;
+	} else if (error_level & LIB_CELL_RENDERER_ERROR_WARN) {
+		/* Only warning set; orange color */
+		color->red = 0.6;
+		color->blue = 0.0;
+		color->green = 0.4;
+	} else {
+		/* Everything okay; green color */
+		color->red = (double)61.0/(double)255.0;
+		color->green = (double)152.0/(double)255.0;
+		color->blue = 0.0;
+	}
+}
+
 static void lib_cell_renderer_set_property(GObject      *object,
 					   guint        param_id,
 					   const GValue *value,
 					   GParamSpec   *pspec)
 {
 	GValue val = G_VALUE_INIT;
-
-	g_value_init(&val, G_TYPE_STRING);
+	GdkRGBA color;
 
 	switch (param_id) {
 	case PROP_LIB:
+		g_value_init(&val, G_TYPE_STRING);
 		g_value_set_string(&val, ((struct gds_library *)g_value_get_pointer(value))->name);
 		g_object_set_property(object, "text", &val);
 		break;
 	case PROP_CELL:
+		g_value_init(&val, G_TYPE_STRING);
 		g_value_set_string(&val, ((struct gds_cell *)g_value_get_pointer(value))->name);
 		g_object_set_property(object, "text", &val);
 		break;
+	case PROP_ERROR_LEVEL:
+		/* Set cell color according to error level */
+		g_value_init(&val, GDK_TYPE_RGBA);
+		convert_error_level_to_color(&color, g_value_get_uint(value));
+		g_value_set_boxed(&val, &color);
+		g_object_set_property(object, "foreground-rgba", &val);
+		break;
 	default:
 		G_OBJECT_WARN_INVALID_PROPERTY_ID(object, param_id, pspec);
 		break;
@@ -89,6 +122,8 @@ void lib_cell_renderer_class_init(LibCellRendererClass *klass)
 	properties[PROP_CELL] = g_param_spec_pointer("gds-cell", "gds-cell",
 							 "Cell reference to be displayed",
 							 G_PARAM_WRITABLE);
+	properties[PROP_ERROR_LEVEL] = g_param_spec_uint("error-level", "error-level",
+							"Error level of this cell", 0, 255, 0, G_PARAM_WRITABLE);
 
 	g_object_class_install_properties(oclass, PROP_COUNT, properties);
 }
diff --git a/tree-renderer/lib-cell-renderer.h b/tree-renderer/lib-cell-renderer.h
index 4e0949f..b71888a 100644
--- a/tree-renderer/lib-cell-renderer.h
+++ b/tree-renderer/lib-cell-renderer.h
@@ -27,6 +27,9 @@ G_BEGIN_DECLS
 G_DECLARE_FINAL_TYPE(LibCellRenderer, lib_cell_renderer, LIB_CELL, RENDERER, GtkCellRendererText)
 #define TYPE_LIB_CELL_RENDERER (lib_cell_renderer_get_type())
 
+#define LIB_CELL_RENDERER_ERROR_WARN (1U<<0)
+#define LIB_CELL_RENDERER_ERROR_ERR (1U<<1)
+
 typedef struct _LibCellRenderer {
         /* Inheritance */
         GtkCellRendererText super;
diff --git a/tree-renderer/tree-store.c b/tree-renderer/tree-store.c
index 2ba5c11..28b3ec7 100644
--- a/tree-renderer/tree-store.c
+++ b/tree-renderer/tree-store.c
@@ -127,7 +127,7 @@ struct tree_stores *setup_cell_selector(GtkTreeView* view, GtkEntry *search_entr
 	stores.base_tree_view = view;
 	stores.search_entry = search_entry;
 
-	stores.base_store = gtk_tree_store_new(CELL_SEL_COLUMN_COUNT, G_TYPE_POINTER, G_TYPE_POINTER, GDK_TYPE_RGBA, G_TYPE_STRING, G_TYPE_STRING);
+	stores.base_store = gtk_tree_store_new(CELL_SEL_COLUMN_COUNT, G_TYPE_POINTER, G_TYPE_POINTER, G_TYPE_UINT, G_TYPE_STRING, G_TYPE_STRING);
 
 	/* Searching */
 	if (search_entry) {
@@ -147,8 +147,8 @@ struct tree_stores *setup_cell_selector(GtkTreeView* view, GtkEntry *search_entr
 	column = gtk_tree_view_column_new_with_attributes("Library", render_lib, "gds-lib", CELL_SEL_LIBRARY, NULL);
 	gtk_tree_view_append_column(view, column);
 
-	/* Cell color: #3D9801 */
-	column = gtk_tree_view_column_new_with_attributes("Cell", render_cell, "gds-cell", CELL_SEL_CELL, "foreground-rgba", CELL_SEL_CELL_COLOR, NULL);
+	column = gtk_tree_view_column_new_with_attributes("Cell", render_cell, "gds-cell", CELL_SEL_CELL,
+							  "error-level", CELL_SEL_CELL_ERROR_STATE, NULL);
 	gtk_tree_view_append_column(view, column);
 
 	column = gtk_tree_view_column_new_with_attributes("Mod. Date", render_dates, "text", CELL_SEL_MODDATE, NULL);
diff --git a/tree-renderer/tree-store.h b/tree-renderer/tree-store.h
index aa6d283..e9b60da 100644
--- a/tree-renderer/tree-store.h
+++ b/tree-renderer/tree-store.h
@@ -37,7 +37,7 @@
 enum cell_store_columns {
         CELL_SEL_LIBRARY = 0,
         CELL_SEL_CELL,
-	CELL_SEL_CELL_COLOR, /**< Cell column color */
+	CELL_SEL_CELL_ERROR_STATE, /**< Used for cell color and selectability */
         CELL_SEL_MODDATE,
         CELL_SEL_ACCESSDATE,
 	CELL_SEL_COLUMN_COUNT /**< Not a column. Used to determine count of coumns **/