[FIX] mail: systray: colors in messaging menu
[FIX] mail: systray: colors in messaging menu

Default color is white in the enterprise webclient since the navbar refactoring
of bf39884.

dfang/odoo,dfang/odoo,ygol/odoo,hip-odoo/odoo,hip-odoo/odoo,ygol/odoo,ygol/odoo,ygol/odoo,hip-odoo/odoo,dfang/odoo,ygol/odoo,hip-odoo/odoo,ygol/odoo,dfang/odoo,dfang/odoo,hip-odoo/odoo,hip-odoo/odoo,ygol/odoo,dfang/odoo