Changing color event calendar css - choise dropdown list form

[buc]

Hello, how can I get a different color for each event in the calendar display?
In this way changes the color to all events, how do I change the color to make more events?
.fabrikEditEvent{
font-size: 16px !important;
background-color: #ffffff !important;
}

I tried to do it this way but I do not get any results?

.rejected .richiesta___stato{
font-size: 16px !important;
background-color: red !important;
}

.approved .richiesta___stato{
font-size: 16px !important;
background-color: green !important;
}

help me please.