Hello Roman,
The color of the constellation labels and lines was indeed changed to a purplish hue in v8.3! I changed it because yellow was clashing with the other markings on the map, like the ecliptic line. Also, since yellow is a bright color, I thought it was unsuitable for constellation lines because they are all over the map and hog all the "limelight" :)
I realize that this choice is very subjective. I will try to make the map colors customizable. It should be easy to implement after I complete the transition to a new UI framework. (About 25% of the transition is already complete and shipping in the 8.5.x releases that are rolling out now.)
cheers,
Harshad