<tree colors="red:notes!=False'">

Take a look at an existing XML definition of a treeview that uses colors for more help.

Hi, try this example...

In py file

'status' : fields.selection([('single','Single'),('married','Married')],'Status?'),

In xml file

<tree string="Status" colors="red:shop=='single';green:shop=='married' "> <field name="name"></field> <field name="status"></field> </tree>

For Odoo 11 in original view:

<tree decoration-success="state=='done'" decoration-success="state=='undone'">

...

</tree>

on inherited view:

<xpath expr="//tree" position="attributes">

    <attribute name="decoration-danger">approved == False</attribute>

    <attribute name="decoration-bf">approved == True</attribute>

   <attribute name="decoration-success">approved == True</attribute>

</xpath>

If you want to compare several values or make operations you can also do something like:

<tree colors="blue:state == 'draft';black:state in ('proforma','proforma2','open');gray:state == 'cancel';orange:date_due &lt; current_date;" string="Invoice" default_order="date_invoice">

take note that in xml you can not use <, >, >=,<= because that simbols are part of the structure, so instead use &lt;, &gt;, &lt;= and &gt;=

Using a decoration tag is a better idea!
There are many defined colors for decoration and we can apply them based on conditions in  tree as well as in fields

If you wanna combine two decorators, can use "or" and "and" operators in the decorator, for example:

decoration-success="state=='offer_received' or state=='offer_accepted'"

I would make it with custom web module.

JS: RPC call with list of ID's from each row from listview

Python controller: response with list of ID's what have note field not empty.

JS: change color for this ID's

For Odoo13, Odoo14, Odoo15 

decoration-danger="color_definer=='0'"