I am sorry to say that currently this functionality is not available in the RadHtmlChart and thus the labels and tooltips cannot have different fonts and sizes. At the current state of affairs only the background color can be changed for the title of the chart, for the legend and for the tooltips of the series. You can find more information about the available configurations in the online demos (e.g. this one
- see the configurators) and in the documentation (its server-side API
The good news is that adding more customization options is in our TODO list and such features will be added, yet at the present moment I cannot provide a time estimate on them.
All the best,
the Telerik team
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