[FIX] mail: systray messaging menu: channel names color
[FIX] mail: systray messaging menu: channel names color

Color was white in the enterprise webclient since the large refactorting of
navbar, but white on white doesn't look good.

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