Hi Antonie,
Thanks for contacting Syncfusion Support.
Query 1: Color customization of individual segment
We can customize the color of individual segment by setting the interior for the corresponding segment in SegmentCreatedEvent of sunburst chart. We have modified the provided sample and it can be downloaded from below link,
Query 2: Regarding UG Documentation
We are currently working on the SfSunburstChart UG documentation and it will be updated in our upcoming Volume 1, 2017 main release
Query 3: Regarding reducing the radius
Currently we don’t have support for customizing the radius for individual levels. However, we have considered this as feature and have added it to our feature request list. The feature will be implemented in any of our upcoming release.
Regards,
Devi