Haven’t tested but a theory: you are using python3!
From https://docs.python.org/3/whatsnew/3.0.html
dict methods dict.keys(), dict.items() and dict.values() return “views” instead of lists. For example, this no longer works: k = d.keys(); k.sort(). Use k = sorted(d) instead (this works in Python 2.5 too and is just as efficient).
as I understand it a “view” is an iterator, and an iterator does not have the sort function. Change it to
sorted(all_colors)
according to the documentation