The blue part of the radio and check buttons is gone in 2017.1.xxx. There is a slight hover highlight, but in general, it is drastically different from the previous version (2016.3.1303).

The new appearance can be seen at

http://demos.telerik.com/aspnet-ajax/radiobuttonlist/examples/overview/defaultcs.aspx?skin=Silk

http://demos.telerik.com/aspnet-ajax/checkboxlist/examples/overview/defaultcs.aspx?skin=Silk 

http://demos.telerik.com/aspnet-ajax/checkbox/overview/defaultcs.aspx?skin=Silk

as well as a comparison between before and after the new release in the attached screenshot.