ACL and Vlan Maps maybe can help you in limiting access to some resources on vlan x from switch perspective;
otherwise, ACLs on router to block access to servers, etc
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there is no concept of password in the VLAN but there are many methods to get the same as:
1. Use the Access list
2. Use the VRF-lite etc.
on a side note, I guess one way to 'hide' specific Vlans would be to use VTP and set the switch with the Vlans you don't want anybody else to access to 'vtp transparent'. That way, the Vlans configured on that switch would stay local.