As an Admin you can add devices and also see all devices of your organization by default. For non-Admin users you can fine granualary adjust who has access to which device. It might be that your colleague is not an admin or has not got the permission to access the added device.
If an editor or viewer cannot see data in dashboards and receives an error with the message “InfluxDB Error: Access to one or more of the given devices not allowed for current user: [‘…’]” in the Time Series Data Service, this is often because the user has the correct role but not the permissions for the devices. You need to give the user access to the devices.
To do this, simply visit the User Management Service and assign the authorization for the device to your colleague.