Hi Oscar,
The best way to think about it is that the VRID defines a VRRP instance, within one VLAN. If all four switches will share one VRRP VIP, then they will need the same VRID configured.
However, if SW1 and SW2 will share one VIP, and SW3 and SW4 will share another VIP, there should be two VRIDs configured. One VRID will be common to SW1 and SW2, and the other VRID will be common to SW3 and SW4.
-Brandon