Hi,
I think it's possible.
Please look at the example.
https://examples2.ext.net/#/Calendar/Overview/Basic/
There are the "Other" group
<CalendarStore ID="CalendarStore1" runat="server">
<Calendars>
<ext:CalendarModel CalendarId="1" Title="Home" />
<ext:CalendarModel CalendarId="2" Title="Work" />
<ext:CalendarModel CalendarId="3" Title="School" />
<ext:CalendarModel CalendarId="4" Title="Other" />
</Calendars>
</CalendarStore>
and these CSS rules:
<style type="text/css">
.ext-color-4,
.ext-ie .ext-color-4-ad,
.ext-opera .ext-color-4-ad {
color: #7F0000;
}
.ext-cal-day-col .ext-color-4,
.ext-dd-drag-proxy .ext-color-4,
.ext-color-4-ad,
.ext-color-4-ad .ext-cal-evm,
.ext-color-4 .ext-cal-picker-icon,
.ext-color-4-x dl,
.ext-color-4-x .ext-cal-evb {
background: #7F0000;
}
.ext-color-4-x .ext-cal-evb,
.ext-color-4-x dl {
border-color: #7C3939;
}
</style>
To override CSS styles of, for example, the second group you should replace "4" with "2".