Oh, I was probably not clear enough what the picture shows :-) It's a part of rainbow so those colors should be there, the problem is the bleak curvy light yellow band curling around in the crop (quite hard to see, requires good screen). I've already applied color cast correction.
The reason there's a rainbow in there is that the problem only seems to occur (become visible at least) when there's saturated colors in out of focus background
Here's another example, probably a bit clearer. Look at the out of focus features especially, there some red and greenish outlines around the violet out of focus flowers.