BCGSuite for MFC
void CBCGPCalendar::SetDateColor ( COleDateTime  date,
COLORREF  color,
BOOL  bRedraw = TRUE 

Sets the color of specified date.

Use this method to assign a special color to the specified date. For example, you may want to mark public holidays by a different, than the default, color.

dateSpecifies the date whose color is changed.
colorSpecifies the new color.
bRedrawIf TRUE, the control will be redrawn to reflect the new state.