There is no need to search for the original AxisYMinorTickStyle. Just place your new style in UserControl.Resources for example and tell the corresponding chart element to use it. As shown in the help topic that my colleague Evgenia provided in the previous post, by placing this:
in your resources, and then telling the Y axis to use it for its minor ticks:
you will get orange minor ticks.
I hope this helps.
All the best,
the Telerik team