The blue relays are Finder, new brown ones are Schrader. I actually suggest that if you have the blue finder relay sockets that you keep the finder relays. The new relay pins are way smaller and I have had problems where they just won’t make a good connection in those bases. If you have blue relays in black bases, by all means, replace them with the new ones but I would save the good blue ones for when you need to replace a blue relay in a blue base. There was a time when Thyssen told everyone to replace the blue relays but I think there was just a bad lot or something. Also compare the contact size on the 2, watch how fast you smoke the new relay contacts on controllers with Maxton valves! And if you see any blue relays that say 5000 on them, they have gold plated contacts.