scooby_doe

Странное использование onclick атрибута и события on, нужно что-то одно. Если с атрибутом onclick, то будет так:

<div class="block">
    <div onclick="ShowDataFilter(this)" class="widget-title cus-category">Цвет<i class="cus-fa fa fa-angle-double-right" aria-hidden="true"></i></div>
    <ul class="cus-slide c-ip-attribute-filter__list" style="display: none">
        <div class="custom-checkbox">    <input class="custom-control-input" type="checkbox" name="brand_0" id="name_0" value="1">    <label for="name_0" class="custom-control-label cus-fw-adminLte-override">Черный (2129)</label></div>
        <div class="custom-checkbox">    <input class="custom-control-input" type="checkbox" name="brand_1" id="name_1" value="1">    <label for="name_1" class="custom-control-label cus-fw-adminLte-override">Синий (910)</label></div>
        <div class="custom-checkbox">    <input class="custom-control-input" type="checkbox" name="brand_2" id="name_2" value="1">    <label for="name_2" class="custom-control-label cus-fw-adminLte-override">Фиолетовый (185)</label></div>
        <div class="custom-checkbox">    <input class="custom-control-input" type="checkbox" name="brand_3" id="name_3" value="1">    <label for="name_3" class="custom-control-label cus-fw-adminLte-override">Серый (696)</label></div>
        <div class="custom-checkbox">    <input class="custom-control-input" type="checkbox" name="brand_4" id="name_4" value="1">    <label for="name_4" class="custom-control-label cus-fw-adminLte-override">Бордовый (168)</label></div>
    </ul>
</div>
<div class="block">
    <div onclick="ShowDataFilter(this)" class="widget-title cus-category">Тип<i class="cus-fa fa fa-angle-double-right" aria-hidden="true"></i></div>
    <ul class="cus-slide c-ip-attribute-filter__list" style="display: none">
        <div class="custom-checkbox">    <input class="custom-control-input" type="checkbox" name="brand_0" id="name_0" value="1">    <label for="name_0" class="custom-control-label cus-fw-adminLte-override">Ободковая (6227)</label></div>
        <div class="custom-checkbox">    <input class="custom-control-input" type="checkbox" name="brand_1" id="name_1" value="1">    <label for="name_1" class="custom-control-label cus-fw-adminLte-override">Лесочная (381)</label></div>
        <div class="custom-checkbox">    <input class="custom-control-input" type="checkbox" name="brand_2" id="name_2" value="1">    <label for="name_2" class="custom-control-label cus-fw-adminLte-override">Безободковая (420)</label></div>
        <div class="custom-checkbox">    <input class="custom-control-input" type="checkbox" name="brand_3" id="name_3" value="1">    <label for="name_3" class="custom-control-label cus-fw-adminLte-override">полуободковые (124)</label></div>
        <div class="custom-checkbox">    <input class="custom-control-input" type="checkbox" name="brand_4" id="name_4" value="1">    <label for="name_4" class="custom-control-label cus-fw-adminLte-override">маска (2)</label></div>
    </ul>
</div>

function ShowDataFilter(cusCategory) {
	$(cusCategory).toggleClass('red').siblings('.cus-slide').slideToggle(0);
}