Do you want to change the colors of the weekend in the Ajax Calendar extender control.
You have to change the behaviour of a AJAX Control Tool Kit in this way.Fllow my method.

add CSS to AjaX Control Tool Kit Solution >> Calendar Folder >> Calendar.css
Add one more line..


.ajax__calendar_container {padding:4px;cursor:default;width:170px;font-size:11px;text-align:center;font-family:tahoma,verdana,helvetica;}
.ajax__calendar_body {height:139px;width:170px;position:relative;overflow:hidden;margin:auto;}
.ajax__calendar_days, .ajax__calendar_months, .ajax__calendar_years {top:0px;left:0px;height:139px;width:170px;position:absolute;text-align:center;margin:auto;}
.ajax__calendar_container TABLE {padding:0px;margin:0px;font-size:11px;}
.ajax__calendar_container TD {padding:0px;margin:0px;font-size:11px;}
.ajax__calendar_header {height:20px;width:100%;}
.ajax__calendar_prev {cursor:pointer;width:15px;height:15px;float:left;background-repeat:no-repeat;background-position:50% 50%;background-image:url(<%=WebResource("AjaxControlToolkit.Calendar.arrow-left.gif")%>);}
.ajax__calendar_next {cursor:pointer;width:15px;height:15px;float:right;background-repeat:no-repeat;background-position:50% 50%;background-image:url(<%=WebResource("AjaxControlToolkit.Calendar.arrow-right.gif")%>);}
.ajax__calendar_title {cursor:pointer;font-weight:bold;}
.ajax__calendar_footer {height:15px;}
.ajax__calendar_today {cursor:pointer;padding-top:3px;}
.ajax__calendar_dayname {height:17px;width:17px;text-align:right;padding:0 2px;}
.ajax__calendar_day {height:17px;width:18px;text-align:right;padding:0 2px;cursor:pointer;}
.ajax__calendar_month {height:44px;width:40px;text-align:center;cursor:pointer;overflow:hidden;}
.ajax__calendar_year {height:44px;width:40px;text-align:center;cursor:pointer;overflow:hidden;}
.ajax__calendar .ajax__calendar_container {border:1px solid #646464;background-color:#ffffff;color:#000000;}
.ajax__calendar .ajax__calendar_footer {border-top:1px solid #f5f5f5;}
.ajax__calendar .ajax__calendar_dayname {border-bottom:1px solid #f5f5f5;}
.ajax__calendar .ajax__calendar_day {border:1px solid #ffffff;}
.ajax__calendar .ajax__calendar_month {border:1px solid #ffffff;}
.ajax__calendar .ajax__calendar_year {border:1px solid #ffffff;}
.ajax__calendar .ajax__calendar_active .ajax__calendar_day {background-color:#edf9ff;border-color:#0066cc;color:#0066cc;}
.ajax__calendar .ajax__calendar_active .ajax__calendar_month {background-color:#edf9ff;border-color:#0066cc;color:#0066cc;}
.ajax__calendar .ajax__calendar_active .ajax__calendar_year {background-color:#edf9ff;border-color:#0066cc;color:#0066cc;}
.ajax__calendar .ajax__calendar_other .ajax__calendar_day {background-color:#ffffff;border-color:#ffffff;color:#646464;}
.ajax__calendar .ajax__calendar_other .ajax__calendar_year {background-color:#ffffff;border-color:#ffffff;color:#646464;}
.ajax__calendar .ajax__calendar_hover .ajax__calendar_day {background-color:#edf9ff;border-color:#daf2fc;color:#0066cc;}
.ajax__calendar .ajax__calendar_hover .ajax__calendar_month {background-color:#edf9ff;border-color:#daf2fc;color:#0066cc;}
.ajax__calendar .ajax__calendar_hover .ajax__calendar_year {background-color:#edf9ff;border-color:#daf2fc;color:#0066cc;}
.ajax__calendar .ajax__calendar_hover .ajax__calendar_title {color:#0066cc;}
.ajax__calendar .ajax__calendar_hover .ajax__calendar_today {color:#0066cc;}
//the upper line is already there.....you have to add this css line
.ajax__calendar .ajax__calendar_new .ajax__calendar_day {color:Red;}



in then CalendarBehavior.js file add code...(modified only bold one) Line Number 1048


for (var week = 0; week < weekrow =" this._daysBody.rows[week];" dayofweek =" 0;" daycell =" weekRow.cells[dayOfWeek].firstChild;" title =" currentDate.localeFormat(" date =" currentDate;" currentdate =" new">

if (dtf.ShortestDayNames[(dayOfWeek + firstDayOfWeek) % 7] == "Su") {
//if sunday then change the color  
Sys.UI.DomElement.addCssClass(dayCell.parentNode, "ajax__calendar_new");  }
if (dtf.ShortestDayNames[(dayOfWeek + firstDayOfWeek) % 7] == "Sa") {
//if saturday then chagne the color  
Sys.UI.DomElement.addCssClass(dayCell.parentNode, "ajax__calendar_new");  }
} }

/// you will find this in _performLayout: function() { 
/// Updates the various views of the calendar to match the current selected and visible dates
/// 
switch (this._mode) {
case "days":



If this helps you please give me your comment and put your new suggestions here.