Dashboard colors - json not working

[vylc]

Instructions on how to specify consistent colors on a dashboard are here:
https://superset.incubator.apache.org/faq.html#is-there-a-way-to-force-the-use-specific-colors

However, doesn't work and gets overwritten on dashboard refresh.

https://superset.incubator.apache.org/faq.html#is-there-a-way-to-force-the-use-specific-colors

Make sure these boxes are checked before submitting your issue - thank you!

• I have checked the superset logs for python stacktraces and included it here as text if there are any.
• I have reproduced the issue with at least the latest released version of superset.
• I have checked the issue tracker for the same issue and I haven't found one similar.

Superset version

Expected results

Actual results

Steps to reproduce

[thunter009]

I am having the same issue and consistently getting 'NoneType' object has no attribute 'strip' error when trying to edit dashboard JSON Metadata that was previously valid--specifically I'm adding a "label_colors" object.

[xtinec]

Fixed by #7027