plotly
diff --git a/‎_plotly_utils/colors/__init__.py‎
Lines changed: 16 additions & 3 deletions b/‎_plotly_utils/colors/__init__.py‎
Lines changed: 16 additions & 3 deletions
@@ -76,6 +76,7 @@
 
 import decimal
 from numbers import Number
+from warnings import warn
 
 from _plotly_utils import exceptions
 
@@ -763,15 +764,27 @@ def hex_to_rgb(value):
         '#FFF'    --> (255, 255, 255)
 
     """
+
+    input_value = value
     value = value.lstrip("#")
     if len(value) == 3:
         value = "".join(c * 2 for c in value)
+    elif len(value) == 4:
+        warn(
+            "4-character hex color provided; 4th character will be ignored."
+            "got {!r}".format(input_value)
+        )
+        value = "".join(c * 2 for c in value)[:6]
+    elif len(value) == 8:
+        warn(
+            "8-character hex color provided; last two characters will be ignored."
+            "got {!r}".format(input_value)
+        )
+        value = value[:6]
     elif len(value) != 6:
-        # Any other length silently produced a tuple of the wrong size: the
-        # section width is len // 3, so "#12345" returned a 5-tuple.
         raise ValueError(
             "hex color must be 3 or 6 hex digits, optionally prefixed with "
-            "'#'; got {!r}".format(value)
+            "'#'; got {!r}".format(input_value)
         )
     return tuple(int(value[i : i + 2], 16) for i in range(0, 6, 2))