PyCharm change file type association

Actually, @CrazyCoder is right: If you accidentally mis-labeled the file, PyCharm remembers it and sets a "pattern" for the new file based on the name.

So go to Settings | Editor | File Types, find the type you accidentally mislabeled and remove it from the "Registered Patterns" list.

For example, I mislabed "osm.py" as text file, so under "Text files" I have:

*.bat
*.cgi
.
.
.
osm.py

Remove it and you get your py file colors back! You can also register a file association where there is no extension. By default this is associated as "Text file".

More on File Types.

See Settings| Editor | File Types.