Add color getter-setter for source wrapper

graphs/wrapper.py

@@ -94,7 +94,18 @@ class BaseWrapper:
 
 
 class SourceWrapper(BaseWrapper):
-    pass
+
+    def __init__(self, item):
+        super().__init__(item)
+        self._color = None
+
+    @property
+    def color(self):
+        return self._color
+
+    @color.setter
+    def color(self, value):
+        self._color = value
 
 
 class TargetWrapper(BaseWrapper):

gui/builtinViewColumns/color.py

@@ -42,7 +42,7 @@ class LineColor(ViewColumn):
 
     def getToolTip(self, stuff):
         if isinstance(stuff, SourceWrapper):
-            return ''
+            return 'Change line color'
         return ''