So in each menu item set it to use flatplus for 1 or use global and set the Joomla! global config to Flatplus.
Next, under each menu item set a page class suffix, I think it's under Page Options?
Then duplicate the below 3 times and replace the .pageclass with the pageclass you specified.
.pageclass #jevents_body .jev_toprow div.previousmonth, .pageclass #jevents_body .jev_toprow div.nextmonth {
background-color: #bf3f3f !important;
border: 1px solid #bf3f3f !important;
}
.pageclass #jevents_body .jev_toprow div.currentmonth {
border-top: 1px solid #bf3f3f !important;
border-bottom: 1px solid #bf3f3f !important;
}
.pageclass #jevents_body .nav-items div.active a, .jev_header2 .active a {
background-color: #bf3f3f !important;
}
.pageclass #jevents_body .nav-items > div {
border-color: #bf3f3f !important;
}
.pageclass .jevtip-tip, .jevtip {
border-color: #bf3f3f !important;
}
.pageclass #jevents_body .nav-items > div a:hover {
border-left-color: #bf3f3f !important;
}
.pageclass #flatcal_minical .flatcal_todaycell a {
background-color: #bf3f3f !important;
border-color: #bf3f3f !important;
}
.pageclass #flatcal_minical .flatcal_todaycell a:hover {
background-color: #FFF !important;
color: #bf3f3f !important;
}
And replace the bf3f3f color code with your color codes.
Many thanks
Tony