Changing the color in kanban could be done by setting a class like that :

<code>
<field name="member_color"/>
.../...
<templates>
.../...
<div t-attf-class="oe_kanban_color_#{kanban_getcolor(record.member_color.raw_value)}" >
.../...
</div>
</code>

I created a functionnl field :
```python
'member_color': fields.function(_check_color, 'Couleur', type="integer")
.../...
def _check_color(self, cr, uid, ids, field_name, arg, context):
        pp = pprint.PrettyPrinter(indent=4)
        res = {}       
        for record in self.browse(cr, uid, ids, context):
            color = 0
            if record.membership_state == u'paid':
                color = 4
            elif record.membership_state == u'invoiced':
                color = 3
            elif record.membership_state == u'canceled':
                color = 3
            elif record.membership_state == u'waiting':
                color = 5
            elif record.membership_state == u'old':
                color= 1
            res[record.id] = color
        return res

```

The principle is that the web  widget that handle Kanban will load the color thanks to its css. Check ".openerp .oe_kanban_view .oe_kanban_color_X" css classes in the web css.
AFAIK The color number is limited to 0->9 caus the js method is designed like this.

Hope it could help