moodle/admin/tool/mfa/styles.css

input.tool-mfa-verification-code,
.tool-mfa-verification-code input {
    /* Some elements must be important to override form element*/
    font-size: 1.5em !important; /* stylelint-disable-line declaration-no-important */
    font-family: monospace;
    text-align: center;
    letter-spacing: 1.0em;
    font-weight: bold;
}

.tool-mfa-factor-choose,
.tool-mfa-factor-choose:hover {
    background-color: #fff;
    border-color: #3584c9;
    border-width: 1px;
    width: 100%;
    border-radius: 0.5rem;
}

.tool-mfa-factor-choose:hover,
.tool-mfa-factor-choose:hover .tool-mfa-factor-choose-text {
    text-decoration: underline;
    color: #094478;
    background-color: #cfe2f2;
}

.mfa-verify-form input[type="submit"] {
    height: 50px;
    font-size: 1.05rem;
}

.mfa-verify-form .invalid-feedback {
    font-weight: 700;
}

.mfa-verify-form .form-group.fitem,
.mfa-verify-form .form-group.fitem > span,
.mfa-verify-form .form-group.fitem > span > input {
    width: 100%;
}