I knitted a cable knit sweater coat with Patons, classic wool. I washed in mashine using cold water wool cyle. It is all stretched out. I then dried in sun a few hours and it looks like the yarn got dark in spots. IOs there any way to shrink sweater a little to get back into shape? Please help! So upset with all the time spent on my beautiful sweater.

Go soak it again and lay it out, smooshing it to the finished measurements you want. Shrinking a wool knit is the same as felting it and you don’t want to do that.

Should I use warm water to shrink more or stick to cold?

As I said above, shrinking = felting and you don’t want to do that. Felting happens when you have a change in water temp plus agitation, not just heat. You can use warm or cold, it doesn’t matter, just need to rewet it.