2483e263_TCL_TK_Command_Reference_Guide__Configure_Option
[Resource Name] selectColor [Resource Class] Background [Description] Specifies a background color to use when the button is selected. If set to empty string, no special color is used. If -indicatoron is true then the color applies to the indicator, if false this color is used as the background for the entire widget when selected. [Configure Option] 
-selectcolor color
TCL/TK Command Reference Guide