You can achieve it using below mentioned CSS, you also refer the following sample. Sample: https://stackblitz.com/edit/react-schedule-change-selected-item-color?file=index.js
Index.css
.e-schedule .e-schedule-toolbar .e-active-view .e-tbar-btn-text,
.e-schedule .e-schedule-toolbar .e-active-view .e-icons,
.e-schedule .e-vertical-view .e-header-cells.e-current-day,
.e-schedule .e-vertical-view .e-clone-time-indicator,
.e-schedule .e-vertical-view .e-current-time {
color: blue;
}
.e-schedule .e-vertical-view .e-current-timeline {
border-top: 1px solid blue;
}
.e-schedule .e-vertical-view .e-previous-timeline {
border-top: 1px dotted blue;
}
.e-schedule .e-month-view .e-current-date .e-date-header,
.e-schedule .e-month-agenda-view .e-current-date .e-date-header {
background-color: blue;
}
.e-schedule .e-month-view .e-date-header-wrap table td.e-current-day,
.e-schedule .e-month-agenda-view .e-date-header-wrap table td.e-current-day {
color: blue;
}
Regards,
Praveenkumar.