.wp-block-button .wp-block-button__link{

    border-radius: 3px;
    background: #5bd2a0;
    color: #fff;
    transition: background-color 0.15s ease-in-out;
    font-size: 14px;
    box-shadow: 0 -1px 0 0 rgba(0, 0, 0, 0.25) inset !important;

}

.wp-block-button .wp-block-button__link:hover{

    background: #3FB4AA;

}