I've developed the Neon Color Scheme and the Python Improved language definition to make Python specifically, and as many other languages as possible, look as good as possible, with as many scopes as possible. It also includes different colors for docstrings and comments:

Here are the entries in the .tmTheme
file for docstrings:
<dict>
<key>name</key>
<string>docstring</string>
<key>scope</key>
<string>string.quoted.double.block, string.docstring, string.quoted.single.block</string>
<key>settings</key>
<dict>
<key>fontStyle</key>
<string>italic</string>
<key>foreground</key>
<string>#218B97</string>
</dict>
</dict>
and regular comments:
<dict>
<key>name</key>
<string>Comment</string>
<key>scope</key>
<string>comment</string>
<key>settings</key>
<dict>
<key>fontStyle</key>
<string>italic</string>
<key>foreground</key>
<string>#7F817E</string>
</dict>
</dict>
And, if you want to make your quotation marks stand out:
<dict>
<key>name</key>
<string>String Quotes</string>
<key>scope</key>
<string>string.quoted punctuation.definition.string.begin, string.quoted punctuation.definition.string.end</string>
<key>settings</key>
<dict>
<key>fontStyle</key>
<string>italic</string>
<key>foreground</key>
<string>#FF07A2</string>
</dict>
</dict>