Follow the steps below to create an attractive kanban card.

1. Add a new model to manage the tags for the library.book.rent model, as follows:

class LibraryRentTags(models.Model):
    _name = 'library.rent.tag'

    name = fields.Char()
    color = fields.Integer()

2. Add basic access rights for the library.rent.tag model, as follows:

acl_book_rent_tags,library.book_rent_tags_default,model_library_rent_tag,,1,0,0,0
acl_book_rent_librarian_tags,library.book_rent_tags_librarian,model_library_rent_tag,group_librarian,1,1,1,1

3. Add new fields in the library.book.rent model, as follows:

    color = fields.Integer()
    popularity = fields.Selection([
        ('no', 'No Demand'),
        ('low', 'Low Demand'),
        ('medium', 'Average Demand'),
        ('high', 'High Demand')], default="no")
    tag_ids = fields.Many2many('library.rent.tag')

4. Add fields in the form view, as follows:

<field name="popularity" widget="priority"/>
<field name="tag_ids" widget="many2many_tags"
    options="{'color_field': 'color', 'no_create_edit': True}"/>

5. Update the kanban view to display colors, tags, and priorities, as shown in the following example:

<kanban default_group_by="stage_id" on_create="quick_create"   
    quick_create_view="my_library.library_book_rent_view_form_minimal">
    <field name="stage_id" />
    <field name="color" />
    <templates>
        <t t-name="kanban-box">
            <div t-attf-class="#{kanban_color(record.color.raw_value)} oe_kanban_global_click">
                <div class="o_dropdown_kanban dropdown">
                    <a class="dropdown-toggle o-no-caret btn" role="button" data-toggle="dropdown">
                        <span class="fa fa-ellipsis-v"/>
                    </a>
                    <div class="dropdown-menu" role="menu">
                        <t t-if="widget.editable">
                            <a role="menuitem" type="edit" class="dropdown-item">Edit</a>
                        </t>
                        <t t-if="widget.deletable">
                            <a role="menuitem" type="delete" class="dropdown-item">Delete</a>
                        </t>
                        <ul class="oe_kanban_colorpicker" data-field="color"/>
                    </div>
                </div>
                <div class="oe_kanban_content">
                    <div class="oe_kanban_card oe_kanban_global_click">
                        <div>
                            <i class="fa fa-user"/>
                            <b>
                                <field name="borrower_id" />
                            </b>
                        </div>
                        <div class="text-muted">
                            <i class="fa fa-book"/>
                            <field name="book_id" />
                        </div>
                        <span class="oe_kanban_list_many2many">
                            <field name="tag_ids" widget="many2many_tags" options="{'color_field': 'color'}"/>
                        </span>
                        <div>
                            <field name="popularity" widget="priority"/>
                        </div>
                    </div>
                </div>
            </div>
        </t>
    </templates>
</kanban>

Restart the server and update the module to apply the changes. Then, click on the plus icon on the column. It will display kanban, as shown in the following figure: