Yellow is normal.
I'll post a couple pictures. First one was "stolen" from the net some place. It was for a calendar ?
Normally the wings are up & it's hard to see. Next one is of one I had.
There are those whom say the broken bars in the tail is a bad thing. Some say it's not a problem. Best birds I've seen had no broken bars.
In the picture of yours, it looks like color(s) run up the legs and chest. This can be a bad thing.
Or is it just dirty ?
Mine had some discolor on the legs & lower belly. It was from roosting & dirt/mud.