odoo-addons/addons/om_account_asset/static/src/scss/account_asset.scss

.o_web_client .o_deprec_lines_toggler {
    color: theme-color('danger');
    &.o_is_posted {
        color: theme-color('success');
    }
    &.o_unposted {
        color: theme-color('warning');
    }
}