converse.js/sass/_toolbar.scss

#conversejs {

    .send-button {
        border-radius: 0;
        bottom: var(--send-button-bottom);
        color: var(--inverse-link-color);
    }

    .chatbox {
        .send-button {
            background-color: var(--chat-head-color);
        }
    }

    .chatroom {
        .send-button {
            background-color: var(--chatroom-head-bg-color);
        }
    }


    converse-chat-toolbar {
        background-color: white;
        box-sizing: border-box;
        color: var(--chat-head-color);
        display: flex;
        justify-content: space-between;
        margin: 0;
        width: 100%;

        .fa, .fa:hover,
        .far, .far:hover,
        .fas, .fas:hover {
            color: var(--chat-head-color);
            font-size: var(--font-size-large);
            svg {
                fill: var(--chat-head-color);
            }
        }
        .unencrypted a,
        .unencrypted {
            color: var(--text-color);
            .toolbar-menu {
                a {
                    color: var(--link-color);
                }
            }
        }

        .toolbar-buttons {
            width: 100%;
            display: inline-block;

            .message-limit {
                padding: 0.5em;
                font-weight: bold;
            }
        }

        button {
            margin-top: 0.4em;
            border: 1px transparent solid;
            background-color: transparent;

            &:disabled .fa {
                color: grey;
                &:hover {
                    color: grey;
                }
                svg, svg:hover {
                    fill: grey;
                }
            }
            &.send-button {
                padding-top: 0.2em;
                padding-bottom: 0.2em;
                margin: 0;
                margin-top: -1px;
            }
        }

        .unverified a,
        .unverified {
            color: #cf5300;
        }
        .private a,
        .private {
            color: #4b7003;
        }
        li {
            cursor: pointer;
            display: inline-block;
            list-style: none;
            padding: 0 0.5em;
            &:hover {
                cursor: pointer;
            }
            .toolbar-menu {
                background-color: #fff;
                bottom: 1.7rem;
                box-shadow: -1px -1px 2px 0 rgba(0, 0, 0, 0.4);
                height: auto;
                margin-bottom: 0;
                min-width: 21rem;
                position: absolute;
                right: 0;
                top: auto;
                z-index: $zindex-dropdown;

                &.otr-menu {
                    left: -6em;
                    min-width: 15rem;

                    &.show {
                        display: flex;
                        flex-direction: column;
                    }
                }

                a {
                    color: var(--link-color);
                }
            }
            &.toggle-otr {
                ul {
                    z-index: 99;
                    li {
                        &:hover {
                            background-color: var(--highlight-color);
                        }
                        display: block;
                        padding: 7px;
                        a {
                            display: block;
                        }
                    }
                }
            }
        }
    }

    .chatbox {
        converse-chat-toolbar {
            border-top: var(--chatbox-message-input-border-top);
            color: var(--chat-head-color);
            background-color: white;
            .fas, .fas:hover,
            .far, .far:hover,
            .fa, .fa:hover {
                color: var(--chat-head-color);
            }
            button {
                &:focus {
                    outline-color: var(--chat-head-color) !important;
                }
            }
        }
    }

    .chatroom {
        converse-chat-toolbar {
            border-top: var(--chatroom-message-input-border-top);
            color: var(--chatroom-head-bg-color);
            .fas, .fas:hover,
            .far, .far:hover,
            .fa, .fa:hover {
                color: var(--chatroom-head-bg-color);
                font-size: var(--font-size-large);
                svg {
                    fill: var(--chatroom-head-bg-color);
                }
            }
            button {
                &:focus {
                    outline-color: var(--chatroom-head-bg-color) !important;
                }
            }
        }
    }
}

#conversejs.converse-overlayed  {
    converse-chat-toolbar {
        li {
            .toolbar-menu {
                min-width: 235px;
            }
        }
    }
    .chatroom {
        converse-chat-toolbar {
            li {
                .toolbar-menu {
                    min-width: 280px;
                }
            }
        }
    }
}