I had the same problem.
Try adding this code
/* um-request-button colors*/
.um .um-field-group-head,
.picker__box,
.picker__nav--prev:hover,
.picker__nav--next:hover,
.um .um-members-pagi span.current,
.um .um-members-pagi span.current:hover,
.um .um-profile-nav-item.active a,
.um .um-profile-nav-item.active a:hover,
.upload,
.um-modal-header,
.um-modal-btn,
.um-modal-btn.disabled,
.um-modal-btn.disabled:hover,
div.uimob800 .um-account-side li a.current,
div.uimob800 .um-account-side li a.current:hover,
.um .um-request-button,
.um a.um-request-button,
.um a.um-request-button.um-disabled:hover,
.um a.um-request-button.um-disabled:focus,
.um a.um-request-button.um-disabled:active,
.um input[type=submit].um-request-button,
.um input[type=submit].um-request-button:focus,
.um input[type=submit]:disabled:hover
{
background: #318168 !important;
}
.um .um-field-group-head:hover,
.picker__footer,
.picker__header,
.picker__day--infocus:hover,
.picker__day--outfocus:hover,
.picker__day--highlighted:hover,
.picker--focused .picker__day--highlighted,
.picker__list-item:hover,
.picker__list-item--highlighted:hover,
.picker--focused .picker__list-item--highlighted,
.picker__list-item--selected,
.picker__list-item--selected:hover,
.picker--focused .picker__list-item--selected,
.um .um-request-button:hover,
.um a.um-request-button:hover,
.um input[type=submit].um-request-button:hover{
background: #3d9c7d !important;
}