diff --git a/discord/ext/commands/converter.py b/discord/ext/commands/converter.py
index 81d3a00ed..13d7e41ca 100644
--- a/discord/ext/commands/converter.py
+++ b/discord/ext/commands/converter.py
@@ -294,6 +294,8 @@ class ColourConverter(Converter):
             arg = arg[1:]
         try:
             value = int(arg, base=16)
+            if not (0 <= value <= 0xFFFFFF):
+                raise BadArgument('Colour "{}" is invalid.'.format(arg))
             return discord.Colour(value=value)
         except ValueError:
             method = getattr(discord.Colour, arg.replace(' ', '_'), None)