diff --git a/discord/colour.py b/discord/colour.py
index e640f9df4..5772b145d 100644
--- a/discord/colour.py
+++ b/discord/colour.py
@@ -196,6 +196,9 @@ class Colour:
             The string could not be converted into a colour.
         """
 
+        if not value:
+            raise ValueError('unknown colour format given')
+
         if value[0] == '#':
             return parse_hex_number(value[1:])