Bulma class: .is-outlined

    <button class="button is-primary is-outlined">Button</button>
    <button class="button is-info is-outlined">Button</button>
    <button class="button is-link is-outlined">Button</button>
    <button class="button is-outlined">Button</button>
    <button class="button is-success is-outlined">Button</button>
    <button class="button is-danger is-outlined">Button</button>