That means your blue PROMs are bad.When the proms were swapped around and the green proms put into the blue sockets, it did not generate green.
The PROMs themselves don't know what color they are... they're just used to control the circuitry behind them. So when you put the (good) "green" PROM in the "blue" PROM socket, you got blue because the rest of the circuity is fine. When you put the (bad) "blue" PROM in the "green" PROM socket, you lost green because the (bad) "blue" PROM wasn't telling the green circuitry to draw anything.
While this is a good troubleshooting test, note that you have to replace it with the correct PROM (they're programmed), or the colors won't look correct. And note that there are both "pink" and "white" label PROMs... you need to make sure you get that correct as well.
@steph from HobbyRoms should be able to burn you the PROMs that you need (also from Canada).
DogP

