Hi Rafael,
Greetings from Syncfusion.
We have validated your reported scenario. As of now, we don’t have support to apply theme color for chart axis scrollbar. We have considered your requirement as improvement and logged a feature request on this. We will include this improvement in our upcoming Volume 4 Main Release which is expected to be rolled out at end of December, 2021. You can keep track of an improvement from the feedback portal below.
If you have any more specification/precise replication procedure or a scenario to be tested, you can add it as a comment in the portal.
Regards,
Durga G