On my 15, the 6GU7 on the right corner of the board closest to the HO tube was the issue. It was causing the entire pixture to go green. In order to make the color straighten out, I had to move that tube around ALOT. It wasn't just a matter of tapping it or rockin it back and forth. And, I could only find this one tiny little position for it to be in and work. Once I got it there, all was good. Finding it was the hard part. Kinda like a boy getting his first piece of... um... well you all know what i mean.
Some of ya'll might even still remember!
Any of the wires that run across the top of the board... check to make sure they look healthy near the solder point. My same 15 had a wire to run heaters across the top of that board... was a little corroded at one end. Come to find out, it was a lot broke, too!
I kinda doubt your problem is a heater connection, but, some of those wires might be for something other than heaters.
As far as other components, you might try taking a pencil eraser and start on the chroma board... push lightly on each capacitor, resister, coil, etc. I found a cracked coil on a color board in my Curtis Mathes that way that caused an occasional loss of blue. When I pushed it one way, blue came in. Mashed it the other way and blue went bye-bye.