You can change the color (or any of the visual attributes) of the ActiveRow by using the UltraGrid.DisplayLayout.Override.ActiveRowAppearance. However, there is no way to know whether the mouse is hovering over the dropdown using only properties of the public object model. If it happens to be a ValueListDropDown control (which is displayed by the standard EditorWithCombo when you use a ValueList), you could probably handle the MouseHover event of that control and set the appearance accordingly. An alternative approach would be to set/modify the ActiveRowAppearance in the BeforeCellListDropDown event (and clear the settings in the AfterCellListCloseUp event). This would require much less code, the disadvantage however being that the appearance will be different when the dropdown is visible, and not only when the mouse hovers over it as you stipulated here.