The ExComboBox control can group the control columns into two categories: locked and unlocked. The Locked category contains all the columns that are fixed to the left area of the client area. These columns cannot be scrolled horizontally. Use the CountLockedColumns to specify the number of locked columns. The unlocked are contains the columns that can be scrolled horizontally. To change the background color of the control's locked area use BackColorLock property. Use the BackColorEdit property to specify the background color of the control's edit box. Use the CellBackColor property to specify the cell's background color. Use the ItemBackColor property to specify the item's background color. Use the HeaderBackColor and HeaderForeColor properties to defines the colors for the control's header bar.