This is on an IBM 5154.
Dark grey next to light grey produces a white line between the two. This is noticeable on a color bar test, but is even worse in SimCity (making the text impossible to read).
If I adjust contrast to the minimum, the white goes away, but then brown is no longer brown and the 'light' colors are identical to the 'dark' colors.
Thoughts on what this might be? I might try adjusting the red cut-off and LSB, since I notice it's on the boundary of where red is when I turn the brightness way down.
Here's SimCity with the blue and green cut-off at minimum:
Edit: I replaced ~9 or so electrolytic capacitors on the video board, all of them in the PSU, and tested those on the CRT board (all good). None that had any effect whatsoever.