property Schedule.SelectEventColor as Color
Indicates the color to show the selected events.

TypeDescription
Color A Color expression that defines color to show the frame around the selected event, or the background color of the event's body 
If the SelectEventStyle property is exNoLines ( by default ), the SelectEventColor / SelectEventTextColor indicates the background / foreground colors to be applied on the event's body. If the SelectEventStyle property is NOT exNoLines, the the SelectEventColor property indicates the color to show the frame around the selected events. In other words, you can use the SelectEventStyle on exLinesSolid + exLinesThick, to display a frame arround the selected events, rather than changing the event's background/foreground colors. The ShowSelectEvent property prevents showing the selected events in a different way (using a frame around, by changing the body's background/foreground colors).

You can use the AllowSelectEvent property to change the key to allow the user select new events or you can prevent selecting any event using exDisallow value.