Hi,

You can set the background color of each record in the tree view

based on a condition by following these steps:

1. Define the condition in the XML file: In the XML file, within the

<tree>

element, you can set the decoration-attributes to define the condition for each background color.

<record id="sale_order_view_tree" model="ir.ui.view">

<field name="name">product.template.view.tree.inherit.sale_order</field>

<field name="model">sale.order</field>

    <field name="inherit_id" ref="sale.view_order_tree"/>

    <field name="arch" type="xml">

        <tree position="attributes">

            <attribute name="decoration-danger">state == draft</attribute>

<attribute name="decoration-success">state== sent</attribute>

<attribute name="decoration-warning">state== sale</attribute>

        </tree>

    </field>

</record>

2. Add CSS styles in the CSS file:

.o_sale_order .text-success { background-color: #a7f2af7d !important;

}

 .o_sale_order

.text-danger { background-color: #fb88847d !important; }

.o_sale_order

.text-warning { background-color: #fdf57d8f !important; }

Hope it helps

Thanks for sharing this link. I was also looking for the same. 

Checkout this module:
https://apps.odoo.com/apps/modules/15.0/web_tree_dynamic_colored_field/