Hi Chris,
thanks for your help! Upon trying to save my plot to my account, I noticed it is actually showing the correct colors there. Playing around some more, I found that within my actual django site it is also showing fine in Firefox and Safari, but not in Chrome.
There are also some other issues I started to realize, e.g. my axis labels not showing in Chrome. However, updating Chrome did actually solve these issues. Sorry for the inconvenience with that.
Another issue is the hovertext background color is black in all tested browsers, while it displays the color of the respective dot, when uploading to my plotly account. But that’s more of a cosmetic issue.
Btw, I am using nedned’s trick from this thread for combining django and dash: https://community.plotly.com/t/django-and-dash-eads-method/7717
tl;dr: Problem solved by updating Chrome 