Fixed display of database color

Closes #2139, closes #2119

datasette/database.py

@@ -1,6 +1,7 @@
 import asyncio
 from collections import namedtuple
 from pathlib import Path
+import hashlib
 import janus
 import queue
 import sys
@@ -62,6 +63,12 @@ class Database:
             }
         return self._cached_table_counts
 
+    @property
+    def color(self):
+        if self.hash:
+            return self.hash[:6]
+        return hashlib.md5(self.name.encode("utf8")).hexdigest()[:6]
+
     def suggest_name(self):
         if self.path:
             return Path(self.path).stem