Hello Everyone, 

I have to try to change string colour near the expiry date.

And expiry show approximate one month before ending date

My code below :

@api.depends('ren9','ren13')
def _compute_default_status(self):
    value = {}
    for rec in self:
        if rec.ren9:
            print "REC:::::::::::", rec.ren15, rec.ren14
            end_date = datetime.strptime(rec.ren15, '%Y-%m-%d')
            expr = end_date - relativedelta(months=1)
            r = relativedelta(end_date, expr)
            print "DATE:::::::::::::::::::,", r, expr, rec.id

            if r < 1 :
                print "noof", rec.id, expr
                if rec.ren17:
                    rec.ren13 = 'near_close'
                    value.update(ren13=rec.ren13)
                    print "NEAR CLOSE::::::::::", rec.ren13
                else:
                    rec.ren13 = 'occupied'
                    value.update(ren13=rec.ren13)
                    print "OCCUPIED::::::::::", rec.ren13
        else:
            rec.ren13 = 'available'
            value.update(ren13=rec.ren13)

and Where 

ren9 = fields.Many2one('res.partner', string='Customer')
ren13 = fields.Selection([('available', 'Available'),
                          ('occupied', 'Occupied'),
                          ('expiry_near','Expiry')], string="Status",
                            dafault='available'
                         , compute='_compute_default_status', store=True)
ren14 = fields.Date('Start Date')
ren15 = fields.Date('End date')
ren16 = fields.Float('Rental Price')
ren17 = fields.Date('Expiry', compute='_calculate_month_expiry')

<tree string="Ren Ser" colors="darkred:ren13 == 'occupied'; darkgreen:ren13 == 'available'; blue:ren13 =='near_close'"/>

Thanks in Advanced