Fixing _get_standard_colors to honor num_colors arguments (#20585)
- [ ] closes #20585
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Hello @atulagrwl! Thanks for updating the PR.





 - In the file [`pandas/tests/plotting/test_series.py`](https://github.com/pandas-dev/pandas/blob/a52582ab7c15eed012fbf874a4c527051e08ff37/pandas/tests/plotting/test_series.py), following are the PEP8 issues :

> [Line 295:42](https://github.com/pandas-dev/pandas/blob/a52582ab7c15eed012fbf874a4c527051e08ff37/pandas/tests/plotting/test_series.py#L295): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','
> [Line 295:50](https://github.com/pandas-dev/pandas/blob/a52582ab7c15eed012fbf874a4c527051e08ff37/pandas/tests/plotting/test_series.py#L295): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','



##### Comment last updated on August 21, 2018 at 10:57 Hours UTC @TomAugspurger - Thanks for quick review. Would really appreciate merging it to master soon (this would be my first contribution to get into master).  tests are failing as well @atulagrwl do you plan on making the changes requested of you above?  I'd love to see this bugfix get merged. Closing as stale. Ping if you'd like to pick back up