Vertical rainbow lines

[Pjaska]

Hello! I have this 6 inch orion 6ad5 color tv. It works normally but some times it shows these faint vertical rainbows.

In smb3 it has them in the end of the level where its black and other parts of the game they are absent(see photos). There are some other games that have it shortly on some scenes and also when i was watching cartoons there were these rainbows at some brown parts of the image. It isnt too bad but my eyes keep looking for it (first it was the purity on red and some blue scenes and now this)

I would like to learn why they are and is it a fault or feature. I have messed around with yoke coil and adjustment rings becouse it had some purity issues when it arrived. It didnt seem to affect it much.

I have three 6 inch tv:s and this orion has these rainbows and on the takt i can see it too (not as bad as orion) and the last one i think its jericho it dosnt have them at all. Also my bigger crt:s dont show these lines at all.