Hi Sharon,
Copy this code in your custom css editor
.content-sidebar .widget input[type="button"],
.content-sidebar .widget input[type="reset"],
.content-sidebar .widget input[type="submit"] {
background-color: #400E73;
border: 0;
color: #fff;
}
.content-sidebar .widget input[type="button"]:hover,
.content-sidebar .widget input[type="button"]:focus,
.content-sidebar .widget input[type="reset"]:hover,
.content-sidebar .widget input[type="reset"]:focus,
.content-sidebar .widget input[type="submit"]:hover,
.content-sidebar .widget input[type="submit"]:focus {
background-color: #400E73;
}
.content-sidebar .widget input[type="button"]:active,
.content-sidebar .widget input[type="reset"]:active,
.content-sidebar .widget input[type="submit"]:active {
background-color: #400E73;
}