Documentation of new shorthand hex color specification.

Author: Patrick Feiring

doc/users/next_whats_new/shorthand_hex_colors.rst

@@ -0,0 +1,6 @@
+3-digit and 4-digit hex colors
+------------------------------
+
+Colors can now be specified using 3-digit or 4-digit hex colors, shorthand for
+the colors obtained by duplicating each character, e.g. ``#123`` is equivalent to
+``#112233`` and  ``#123a`` is equivalent to ``#112233aa``.

lib/matplotlib/colors.py

@@ -40,6 +40,10 @@
   interval ``[0, 1]`` (e.g., ``(0.1, 0.2, 0.5)`` or ``(0.1, 0.2, 0.5, 0.3)``);
 * a hex RGB or RGBA string (e.g., ``'#0f0f0f'`` or ``'#0f0f0f80'``;
   case-insensitive);
+* a shorthand hex RGB or RGBA string, equivalent to the hex RGB or RGBA
+  string obtained by duplicating each character, (e.g., ``'#abc'``, equivalent
+  to ``'#aabbcc'``, or ``'#abcd'``, equivalent to ``'#aabbccdd'``;
+  case-insensitive);
 * a string representation of a float value in ``[0, 1]`` inclusive for gray
   level (e.g., ``'0.5'``);
 * one of ``{'b', 'g', 'r', 'c', 'm', 'y', 'k', 'w'}``, they are the single

tutorials/colors/colors.py

@@ -9,6 +9,10 @@
   interval ``[0, 1]`` (e.g., ``(0.1, 0.2, 0.5)`` or ``(0.1, 0.2, 0.5, 0.3)``);
 * a hex RGB or RGBA string (e.g., ``'#0f0f0f'`` or ``'#0f0f0f80'``;
   case-insensitive);
+* a shorthand hex RGB or RGBA string, equivalent to the hex RGB or RGBA
+  string obtained by duplicating each character, (e.g., ``'#abc'``, equivalent
+  to ``'#aabbcc'``, or ``'#abcd'``, equivalent to ``'#aabbccdd'``;
+  case-insensitive);
 * a string representation of a float value in ``[0, 1]`` inclusive for gray
   level (e.g., ``'0.5'``);
 * one of ``{'b', 'g', 'r', 'c', 'm', 'y', 'k', 'w'}``, they are the single