The idea behind a single series is that all items are colored the same way so they are easily distinguishable. This means that such a feature is not supported for the time being and what I can advise is the following:
- follow the PITS item to see when it is available: http://www.telerik.com/support/pits.aspx#/public/aspnet-ajax/12252
- create the items programmatically and add the ones above your threshold to a different series that has the desired color set instead of the default one. Note that this will leave a gap next to all items because there are two series. Thus you will have zero items for all items in the series where a column should not be shown.
the Telerik team
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