https://www.telerik.com/products/winforms/documentation/controls/editors/textboxcontrol/autocomplete
WinForms Editors TextBoxControl AutoComplete - Telerik UI for WinForms
Learn how you can use the auto-complete functionality of WinForms RadTextBoxControl.
winformseditorstextboxcontrolautocompletetelerik
https://www.telerik.com/products/winforms/documentation/controls/editors/textboxcontrol/design-time
WinForms Editors TextBoxControl Design Time - Telerik UI for WinForms
RadTextBoxControl is a text box which supports text formating and auto-complete.
design timewinformseditorstextboxcontroltelerik
https://www.telerik.com/products/winforms/documentation/controls/editors/textboxcontrol/customizing-appearance/themes
WinForms Editors TextBoxControl Customizing Appearance Themes - Telerik UI for WinForms
This article shows how you can the disabled state color in Visual Style Builder.
customizing appearancewinformseditorstextboxcontrolthemes