I just recapped both monitors in my PC-10 and shortly thereafter I have an all green screen. tapping on the cabinet reveals that there was cold solder somewhere.... so I reflowed all the transistors on the neckboard, fixed that.
then I did the top monitor, same shit again. but this time it was the inverter board.
so reflow the transistors on the neckboard first, and if there's an inverter board reflow the headers, pots, etc. on it.
do the pots on the neckboard too. lol
I don't think it's very likely that you just lost all those colors suddenly in the tube.
try tapping the side of the cab first. if it goes apeshit, then you're looking at cold solder. additionally, try reseating the RGB header plug (if you have it like that)