Hello, Tamil,

Note that the look of RadControls is defined through the themes and it may differ from the look of the standard MS controls. Different themes offer different style settings. According to the attached picture with RadDropDownList, it seems that you are using the ControlDefault theme. However, it is important to know which is the specific theme that you use in order to apply proper styling. If you are using any custom theme it would be greatly appreciated if you can specify it.

It is possible to change the style for a specific element state without losing the applied style for the rest of the states by overriding theme settings at run time. For example, when using the ControlDefault theme you can override the "ContainsFocus" state of the drop-down list and change the ForeColor property of the BorderPrimitive as demonstrated below:

this.radDropDownList1.DropDownListElement.SetThemeValueOverride(BorderPrimitive.ForeColorProperty, Color.Orange, "ContainsFocus", typeof(BorderPrimitive));

More information is available here: https://docs.telerik.com/devtools/winforms/telerik-presentation-framework/override-theme-settings-at-run-time 

Another possible approach is to modify the theme directly with the Visual Style Builder tool and achieve the desired look.

I hope this helps. Should you have other questions please let me know.

Regards,
Nadya
Progress Telerik